The Collaborative International Dictionary of English v.0.48:

Pillar \Pil"lar\, a. (Mach.)
   Having a support in the form of a pillar, instead of legs;
   as, a pillar drill.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pillar \Pil"lar\, n. [OE. pilerF. pilier, LL. pilare, pilarium,
   pilarius, fr. L. pila a pillar. See Pile a heap.]
   1. The general and popular term for a firm, upright,
      insulated support for a superstructure; a pier, column, or
      post; also, a column or shaft not supporting a
      superstructure, as one erected for a monument or an
      ornament.
      [1913 Webster]

            Jacob set a pillar upon her grave.    --Gen. xxxv.
                                                  20.
      [1913 Webster]

            The place . . . vast and proud,
            Supported by a hundred pillars stood. --Dryden.
      [1913 Webster]

   2. Figuratively, that which resembles such a pillar in
      appearance, character, or office; a supporter or mainstay;
      as, the Pillars of Hercules; a pillar of the state. "You
      are a well-deserving pillar." --Shak.
      [1913 Webster]

            By day a cloud, by night a pillar of fire. --Milton.
      [1913 Webster]

   3. (R. C. Ch.) A portable ornamental column, formerly carried
      before a cardinal, as emblematic of his support to the
      church. [Obs.] --Skelton.
      [1913 Webster]

   4. (Man.) The center of the volta, ring, or manege ground,
      around which a horse turns.
      [1913 Webster]

   From pillar to post, hither and thither; to and fro; from
      one place or predicament to another; backward and forward.
      [Colloq.]

   Pillar saint. See Stylite.

   Pillars of the fauces. See Fauces, 1.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pillar
    n 1: a fundamental principle or practice; "science eroded the
         pillars of superstition"
    2: anything that approximates the shape of a column or tower;
       "the test tube held a column of white powder"; "a tower of
       dust rose above the horizon"; "a thin pillar of smoke
       betrayed their campsite" [syn: column, tower, pillar]
    3: a prominent supporter; "he is a pillar of the community"
       [syn: pillar, mainstay]
    4: a vertical cylindrical structure standing alone and not
       supporting anything (such as a monument) [syn: column,
       pillar]
    5: (architecture) a tall vertical cylindrical structure standing
       upright and used to support a structure [syn: column,
       pillar]

Moby Thesaurus II by Grady Ward, 1.0:

152 Moby Thesaurus words for "pillar":
   antenna tower, arcade, arch, atlas, backbone, baluster, balustrade,
   banister, barbican, barrel, barrow, base, bedrock, belfry,
   bell tower, bole, boundary stone, brass, bust, cairn, campanile,
   caryatid, cask, cenotaph, champion, colonnade, colonnette,
   colossus, column, cromlech, cross, cup, cupola, cyclolith,
   cylinder, cylindroid, dado, defender, derrick, die, dolmen, dome,
   drum, fire tower, footstalk, footstone, foundation, grave,
   gravestone, headstone, hoarstone, inscription, jack, lantern,
   leader, lighthouse, mainstay, marker, martello, martello tower,
   mast, mausoleum, megalith, memento, memorial, memorial arch,
   memorial column, memorial statue, memorial stone, menhir, minaret,
   monolith, monument, mound, necrology, newel-post, obelisk,
   obituary, observation tower, pagoda, patron, patroness, pedestal,
   pedicel, peduncle, peristyle, pier, pilaster, pile, piling,
   pinnacle, pipe, plaque, plinth, pole, portico, post, prize, prop,
   protector, protectress, pylon, pyramid, queen-post, reliquary,
   remembrance, ribbon, rock, roll, roller, rostral column, rouleau,
   safekeeper, shaft, shrine, sinews, skyscraper, socle, spire, staff,
   stalk, stanchion, stand, standard, standpipe, steeple, stela, stem,
   stone, stupa, subbase, supporter, surbase, tablet, telamon,
   television mast, testimonial, tomb, tombstone, tope, tour, tower,
   tower of strength, trophy, trunk, tube, turret, upholder, upright,
   water tower, windmill tower, worthy



Easton's 1897 Bible Dictionary:

Pillar
   used to support a building (Judg. 16:26, 29); as a trophy or
   memorial (Gen. 28:18; 35:20; Ex. 24:4; 1 Sam. 15:12, A.V.,
   "place," more correctly "monument," or "trophy of victory," as
   in 2 Sam. 18:18); of fire, by which the Divine Presence was
   manifested (Ex. 13:2). The "plain of the pillar" in Judg. 9:6
   ought to be, as in the Revised Version, the "oak of the pillar",
   i.e., of the monument or stone set up by Joshua (24:26).