The Collaborative International Dictionary of English v.0.48:

Tree \Tree\ (tr[=e]), n. [OE. tree, tre, treo, AS. tre['o],
   tre['o]w, tree, wood; akin to OFries. tr[=e], OS. treo, trio,
   Icel. tr[=e], Dan. trae, Sw. tr[aum], tr[aum]d, Goth. triu,
   Russ. drevo, W. derw an oak, Ir. darag, darog, Gr. dry^s a
   tree, oak, do`ry a beam, spear shaft, spear, Skr. dru tree,
   wood, d[=a]ru wood. [root]63, 241. Cf. Dryad, Germander,
   Tar, n., Trough.]
   [1913 Webster]
   1. (Bot.) Any perennial woody plant of considerable size
      (usually over twenty feet high) and growing with a single
      trunk.
      [1913 Webster]

   Note: The kind of tree referred to, in any particular case,
         is often indicated by a modifying word; as forest tree,
         fruit tree, palm tree, apple tree, pear tree, etc.
         [1913 Webster]

   2. Something constructed in the form of, or considered as
      resembling, a tree, consisting of a stem, or stock, and
      branches; as, a genealogical tree.
      [1913 Webster]

   3. A piece of timber, or something commonly made of timber;
      -- used in composition, as in axletree, boottree,
      chesstree, crosstree, whiffletree, and the like.
      [1913 Webster]

   4. A cross or gallows; as Tyburn tree.
      [1913 Webster]

            [Jesus] whom they slew and hanged on a tree. --Acts
                                                  x. 39.
      [1913 Webster]

   5. Wood; timber. [Obs.] --Chaucer.
      [1913 Webster]

            In a great house ben not only vessels of gold and of
            silver but also of tree and of earth. --Wyclif (2
                                                  Tim. ii. 20).
      [1913 Webster]

   6. (Chem.) A mass of crystals, aggregated in arborescent
      forms, obtained by precipitation of a metal from solution.
      See Lead tree, under Lead.
      [1913 Webster]

   Tree bear (Zool.), the raccoon. [Local, U. S.]

   Tree beetle (Zool.) any one of numerous species of beetles
      which feed on the leaves of trees and shrubs, as the May
      beetles, the rose beetle, the rose chafer, and the
      goldsmith beetle.

   Tree bug (Zool.), any one of numerous species of
      hemipterous insects which live upon, and suck the sap of,
      trees and shrubs. They belong to Arma, Pentatoma,
      Rhaphigaster, and allied genera.

   Tree cat (Zool.), the common paradoxure (Paradoxurus
      musang).

   Tree clover (Bot.), a tall kind of melilot (Melilotus
      alba). See Melilot.

   Tree crab (Zool.), the purse crab. See under Purse.

   Tree creeper (Zool.), any one of numerous species of
      arboreal creepers belonging to Certhia, Climacteris,
      and allied genera. See Creeper, 3.

   Tree cricket (Zool.), a nearly white arboreal American
      cricket (Ecanthus niv[oe]us) which is noted for its loud
      stridulation; -- called also white cricket.

   Tree crow (Zool.), any one of several species of Old World
      crows belonging to Crypsirhina and allied genera,
      intermediate between the true crows and the jays. The tail
      is long, and the bill is curved and without a tooth.

   Tree dove (Zool.) any one of several species of East Indian
      and Asiatic doves belonging to Macropygia and allied
      genera. They have long and broad tails, are chiefly
      arboreal in their habits, and feed mainly on fruit.

   Tree duck (Zool.), any one of several species of ducks
      belonging to Dendrocygna and allied genera. These ducks
      have a long and slender neck and a long hind toe. They are
      arboreal in their habits, and are found in the tropical
      parts of America, Africa, Asia, and Australia.

   Tree fern (Bot.), an arborescent fern having a straight
      trunk, sometimes twenty or twenty-five feet high, or even
      higher, and bearing a cluster of fronds at the top. Most
      of the existing species are tropical.

   Tree fish (Zool.), a California market fish (Sebastichthys
      serriceps).

   Tree frog. (Zool.)
      (a) Same as Tree toad.
      (b) Any one of numerous species of Old World frogs
          belonging to Chiromantis, Rhacophorus, and allied
          genera of the family Ranidae. Their toes are
          furnished with suckers for adhesion. The flying frog
          (see under Flying) is an example.

   Tree goose (Zool.), the bernicle goose.

   Tree hopper (Zool.), any one of numerous species of small
      leaping hemipterous insects which live chiefly on the
      branches and twigs of trees, and injure them by sucking
      the sap. Many of them are very odd in shape, the prothorax
      being often prolonged upward or forward in the form of a
      spine or crest.

   Tree jobber (Zool.), a woodpecker. [Obs.]

   Tree kangaroo. (Zool.) See Kangaroo.

   Tree lark (Zool.), the tree pipit. [Prov. Eng.]

   Tree lizard (Zool.), any one of a group of Old World
      arboreal lizards (formerly grouped as the Dendrosauria)
      comprising the chameleons; also applied to various lizards
      belonging to the families Agamidae or Iguanidae,
      especially those of the genus Urosaurus, such as the
      lined tree lizard (Urosaurus ornatus) of the
      southwestern U.S.

   Tree lobster. (Zool.) Same as Tree crab, above.

   Tree louse (Zool.), any aphid; a plant louse.

   Tree moss. (Bot.)
      (a) Any moss or lichen growing on trees.
      (b) Any species of moss in the form of a miniature tree.


   Tree mouse (Zool.), any one of several species of African
      mice of the subfamily Dendromyinae. They have long claws
      and habitually live in trees.

   Tree nymph, a wood nymph. See Dryad.

   Tree of a saddle, a saddle frame.

   Tree of heaven (Bot.), an ornamental tree (Ailantus
      glandulosus) having long, handsome pinnate leaves, and
      greenish flowers of a disagreeable odor.

   Tree of life (Bot.), a tree of the genus Thuja; arbor
      vitae.

   Tree onion (Bot.), a species of garlic (Allium
      proliferum) which produces bulbs in place of flowers, or
      among its flowers.

   Tree oyster (Zool.), a small American oyster (Ostrea
      folium) which adheres to the roots of the mangrove tree;
      -- called also raccoon oyster.

   Tree pie (Zool.), any species of Asiatic birds of the genus
      Dendrocitta. The tree pies are allied to the magpie.

   Tree pigeon (Zool.), any one of numerous species of
      longwinged arboreal pigeons native of Asia, Africa, and
      Australia, and belonging to Megaloprepia, Carpophaga,
      and allied genera.

   Tree pipit. (Zool.) See under Pipit.

   Tree porcupine (Zool.), any one of several species of
      Central and South American arboreal porcupines belonging
      to the genera Chaetomys and Sphingurus. They have an
      elongated and somewhat prehensile tail, only four toes on
      the hind feet, and a body covered with short spines mixed
      with bristles. One South American species (Sphingurus
      villosus) is called also couiy; another (Sphingurus
      prehensilis) is called also c[oe]ndou.

   Tree rat (Zool.), any one of several species of large
      ratlike West Indian rodents belonging to the genera
      Capromys and Plagiodon. They are allied to the
      porcupines.

   Tree serpent (Zool.), a tree snake.

   Tree shrike (Zool.), a bush shrike.

   Tree snake (Zool.), any one of numerous species of snakes
      of the genus Dendrophis. They live chiefly among the
      branches of trees, and are not venomous.

   Tree sorrel (Bot.), a kind of sorrel (Rumex Lunaria)
      which attains the stature of a small tree, and bears
      greenish flowers. It is found in the Canary Islands and
      Tenerife.

   Tree sparrow (Zool.) any one of several species of small
      arboreal sparrows, especially the American tree sparrow
      (Spizella monticola), and the common European species
      (Passer montanus).

   Tree swallow (Zool.), any one of several species of
      swallows of the genus Hylochelidon which lay their eggs
      in holes in dead trees. They inhabit Australia and
      adjacent regions. Called also martin in Australia.

   Tree swift (Zool.), any one of several species of swifts of
      the genus Dendrochelidon which inhabit the East Indies
      and Southern Asia.

   Tree tiger (Zool.), a leopard.

   Tree toad (Zool.), any one of numerous species of
      amphibians belonging to Hyla and allied genera of the
      family Hylidae. They are related to the common frogs and
      toads, but have the tips of the toes expanded into suckers
      by means of which they cling to the bark and leaves of
      trees. Only one species (Hyla arborea) is found in
      Europe, but numerous species occur in America and
      Australia. The common tree toad of the Northern United
      States (Hyla versicolor) is noted for the facility with
      which it changes its colors. Called also tree frog. See
      also Piping frog, under Piping, and Cricket frog,
      under Cricket.

   Tree warbler (Zool.), any one of several species of
      arboreal warblers belonging to Phylloscopus and allied
      genera.

   Tree wool (Bot.), a fine fiber obtained from the leaves of
      pine trees.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tree \Tree\, v. t. [imp. & p. p. Treed; p. pr. & vb. n.
   Treeing.]
   1. To drive to a tree; to cause to ascend a tree; as, a dog
      trees a squirrel. --J. Burroughs.
      [1913 Webster]

   2. To place upon a tree; to fit with a tree; to stretch upon
      a tree; as, to tree a boot. See Tree, n., 3.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tree
    n 1: a tall perennial woody plant having a main trunk and
         branches forming a distinct elevated crown; includes both
         gymnosperms and angiosperms
    2: a figure that branches from a single root; "genealogical
       tree" [syn: tree, tree diagram]
    3: English actor and theatrical producer noted for his lavish
       productions of Shakespeare (1853-1917) [syn: Tree, Sir
       Herbert Beerbohm Tree]
    v 1: force a person or an animal into a position from which he
         cannot escape [syn: corner, tree]
    2: plant with trees; "this lot should be treed so that the house
       will be shaded in summer"
    3: chase an animal up a tree; "the hunters treed the bear with
       dogs and killed it"; "her dog likes to tree squirrels"
    4: stretch (a shoe) on a shoetree [syn: tree, shoetree]

Moby Thesaurus II by Grady Ward, 1.0:

160 Moby Thesaurus words for "tree":
   Stammbaum, acacia, ailanthus, alder, alligator pear, allspice,
   almond, apple, apricot, ash, aspen, avocado, ax, balsa, balsam,
   banyan, bare pole, basswood, bay, bayberry, beech, betel palm,
   birch, block, bottle up, buckeye, butternut, buttonwood, cacao,
   candleberry, cashew, cassia, catalpa, cherry, chestnut, chinquapin,
   cinnamon, citron, clove, coconut, collar, conifer, cork oak,
   corner, cross, cypress, death chair, death chamber, dogwood, drop,
   ebony, elder, electric chair, elm, eucalyptus, evergreen,
   family tree, fig, fir, frankincense, fruit tree, gallows,
   gallows-tree, gas chamber, genealogical tree, genealogy, gibbet,
   grapefruit, guava, guillotine, gum, halter, hardwood tree,
   hawthorn, hazel, hemlock, hemp, hempen collar, henna, hickory,
   holly, hop tree, horse chestnut, hot seat, ironwood, juniper,
   kumquat, laburnum, lancewood, larch, laurel, lemon, lethal chamber,
   lime, linden, litchi, litchi nut, locust, logwood, magnolia,
   mahogany, maiden, mango, mangrove, maple, mast, medlar,
   mountain ash, mulberry, noose, nutmeg, oak, olive, orange, palm,
   papaw, papaya, peach, pear, pecan, pedigree, persimmon, pine,
   pistachio, plane, plum, pole, pollard, pomegranate, poplar, quince,
   raffia palm, rain tree, redwood, rope, sandalwood, sapling,
   sassafras, scaffold, seedling, senna, sequoia, shade tree,
   softwood tree, spar, spruce, stake, stemma, stick, sycamore,
   tangerine, teak, the chair, timber, timber tree, tulip tree,
   walnut, willow, witch hazel, yew



The Free On-line Dictionary of Computing (30 December 2018):

tree

    A directed acyclic graph; i.e. a graph
   wherein there is only one route between any pair of nodes,
   and there is a notion of "toward top of the tree" (i.e. the
   root node), and its opposite direction, toward the leaves.
   A tree with n nodes has n-1 edges.

   Although maybe not part of the widest definition of a tree, a
   common constraint is that no node can have more than one
   parent.  Moreover, for some applications, it is necessary to
   consider a node's daughter nodes to be an ordered list,
   instead of merely a set.

   As a data structure in computer programs, trees are used in
   everything from B-trees in databases and file systems, to
   game trees in game theory, to syntax trees in a human or
   computer languages.

   (1998-11-12)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

TREE. A woody plant, which in respect of thickness and height grows greater
than any other plant.
     2. Trees are part of the real estate while growing, and before they are
severed from the freehold; but as soon as they are cut down, they are
personal property.
     3. Some trees are timber trees, while others do not bear that
denomination. Vide Timber, and 2 Bl. Com. 281.
     4. Trees belong to the owner of the land where they grow, but if the
roots go out of one man's land into that of another, or the branches spread
over the adjoining estates, such roots or branches may be cut off by the
owner of the land into which they thus grow. Rolle's R. 394; 3 Bulst. 198;
Vin. Ab. Trees, E; and tit. Nuisance, W 2, pl. 3; 8 Com. Dig. 983; 2 Com.
Dig. 274; 10 Vin. Ab. 142; 20 Viii. Ab. 415; 22 Vin. Ab. 583; 1 Supp. to
Ves. jr. 138; 2 Supp. to Ves. jr. 162, 448; 6 Ves. 109.
     5. When the roots grow into the adjoining land, the owner of such land
may lawfully claim a right to hold the tree in common with the owner of the
land where it was planted; but if the branches only overshadow the adjoining
land, and the root does not enter it, the tree wholly belongs owner of the
estate where the roots grow. 1 Swift's Dig. 104; 1 Hill. Ab. 6; 1 Ld. Raym.
737. Vide 13 Pick. R. 44; 1 Pick., R. 224; 4 Mass. R. 266; 6 N. H. Rep. 430;
3 Day, 476; 11 Co. 50; Rob. 316; 2 Rolle, It. 141 Moo. & Mal. 112; 11 Conn.
R. 177; 7 Conn. 125; 8 East, R. 394; 5 B. & Ald. 600; 1 Chit. Gen. Pr. 625;
2 Phil. Ev. 138; Gale & Wheat. on Easem. 210; Code Civ. art. 671; Pardes.
Tr. des Servitudes, 297; Bro. Ab. Demand, 20; Dall. Dict. mot Servitudes,
art. 3 Sec. 8; 2 P. Wms. 606; Moor, 812; Hob. 219; Plowd. 470; 5 B. & C.
897; S. C. 8 D. & R. 651. When the tree grows directly on the boundary line,
so that the line passes through it, it is the property of both owners,
whether it be marked as a boundary or not. 12 N. H. Rep. 454.



The Devil's Dictionary (1881-1906):

TREE, n.  A tall vegetable intended by nature to serve as a penal
apparatus, though through a miscarriage of justice most trees bear
only a negligible fruit, or none at all.  When naturally fruited, the
tree is a beneficient agency of civilization and an important factor
in public morals.  In the stern West and the sensitive South its fruit
(white and black respectively) though not eaten, is agreeable to the
public taste and, though not exported, profitable to the general
welfare.  That the legitimate relation of the tree to justice was no
discovery of Judge Lynch (who, indeed, conceded it no primacy over the
lamp-post and the bridge-girder) is made plain by the following
passage from Morryster, who antedated him by two centuries:

        While in yt londe I was carried to see ye Ghogo tree, whereof
    I had hearde moch talk; but sayynge yt I saw naught remarkabyll in
    it, ye hed manne of ye villayge where it grewe made answer as
    followeth:
        "Ye tree is not nowe in fruite, but in his seasonne you shall
    see dependynge fr. his braunches all soch as have affroynted ye
    King his Majesty."
        And I was furder tolde yt ye worde "Ghogo" sygnifyeth in yr
    tong ye same as "rapscal" in our owne.
                                               _Trauvells in ye Easte_