The Collaborative International Dictionary of English v.0.48:

Kat \Kat\ (k[aum]t), n. (Bot.)
   An Arabian shrub (Catha edulis) the leaves of which are
   used as tea by the Arabs.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tea \Tea\ (t[=e]), n. [Chin. tsh[=a], Prov. Chin. te: cf. F.
   th['e].]
   1. The prepared leaves of a shrub, or small tree (Thea
      Chinensis or Camellia Chinensis). The shrub is a native
      of China, but has been introduced to some extent into some
      other countries.
      [1913 Webster]

   Note: Teas are classed as green or black, according to their
         color or appearance, the kinds being distinguished also
         by various other characteristic differences, as of
         taste, odor, and the like. The color, flavor, and
         quality are dependent upon the treatment which the
         leaves receive after being gathered. The leaves for
         green tea are heated, or roasted slightly, in shallow
         pans over a wood fire, almost immediately after being
         gathered, after which they are rolled with the hands
         upon a table, to free them from a portion of their
         moisture, and to twist them, and are then quickly
         dried. Those intended for black tea are spread out in
         the air for some time after being gathered, and then
         tossed about with the hands until they become soft and
         flaccid, when they are roasted for a few minutes, and
         rolled, and having then been exposed to the air for a
         few hours in a soft and moist state, are finally dried
         slowly over a charcoal fire. The operation of roasting
         and rolling is sometimes repeated several times, until
         the leaves have become of the proper color. The
         principal sorts of green tea are Twankay, the poorest
         kind; Hyson skin, the refuse of Hyson; Hyson, Imperial,
         and Gunpowder, fine varieties; and Young Hyson, a
         choice kind made from young leaves gathered early in
         the spring. Those of black tea are Bohea, the poorest
         kind; Congou; Oolong; Souchong, one of the finest
         varieties; and Pekoe, a fine-flavored kind, made
         chiefly from young spring buds. See Bohea, Congou,
         Gunpowder tea, under Gunpowder, Hyson, Oolong,
         and Souchong. --K. Johnson. --Tomlinson.
         [1913 Webster]

   Note: "No knowledge of . . . [tea] appears to have reached
         Europe till after the establishment of intercourse
         between Portugal and China in 1517. The Portuguese,
         however, did little towards the introduction of the
         herb into Europe, and it was not till the Dutch
         established themselves at Bantam early in 17th century,
         that these adventurers learned from the Chinese the
         habit of tea drinking, and brought it to Europe."
         --Encyc. Brit.
         [1913 Webster]

   2. A decoction or infusion of tea leaves in boiling water;
      as, tea is a common beverage.
      [1913 Webster]

   3. Any infusion or decoction, especially when made of the
      dried leaves of plants; as, sage tea; chamomile tea;
      catnip tea.
      [1913 Webster]

   4. The evening meal, at which tea is usually served; supper.
      [1913 Webster]

   Arabian tea, the leaves of Catha edulis; also (Bot.), the
      plant itself. See Kat.

   Assam tea, tea grown in Assam, in India, originally brought
      there from China about the year 1850.

   Australian tea, or Botany Bay tea (Bot.), a woody
      climbing plant (Smilax glycyphylla).

   Brazilian tea.
      (a) The dried leaves of Lantana pseodothea, used in
          Brazil as a substitute for tea.
      (b) The dried leaves of Stachytarpheta mutabilis, used
          for adulterating tea, and also, in Austria, for
          preparing a beverage.

   Labrador tea. (Bot.) See under Labrador.

   New Jersey tea (Bot.), an American shrub, the leaves of
      which were formerly used as a substitute for tea; redroot.
      See Redroot.

   New Zealand tea. (Bot.) See under New Zealand.

   Oswego tea. (Bot.) See Oswego tea.

   Paraguay tea, mate. See 1st Mate.

   Tea board, a board or tray for holding a tea set.

   Tea bug (Zool.), an hemipterous insect which injures the
      tea plant by sucking the juice of the tender leaves.

   Tea caddy, a small box for holding tea.

   Tea chest, a small, square wooden case, usually lined with
      sheet lead or tin, in which tea is imported from China.

   Tea clam (Zool.), a small quahaug. [Local, U. S.]

   Tea garden, a public garden where tea and other
      refreshments are served.

   Tea plant (Bot.), any plant, the leaves of which are used
      in making a beverage by infusion; specifically, Thea
      Chinensis, from which the tea of commerce is obtained.

   Tea rose (Bot.), a delicate and graceful variety of the
      rose (Rosa Indica, var. odorata), introduced from China,
      and so named from its scent. Many varieties are now
      cultivated.

   Tea service, the appurtenances or utensils required for a
      tea table, -- when of silver, usually comprising only the
      teapot, milk pitcher, and sugar dish.

   Tea set, a tea service.

   Tea table, a table on which tea furniture is set, or at
      which tea is drunk.

   Tea taster, one who tests or ascertains the quality of tea
      by tasting.

   Tea tree (Bot.), the tea plant of China. See Tea plant,
      above.

   Tea urn, a vessel generally in the form of an urn or vase,
      for supplying hot water for steeping, or infusing, tea.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Catha edulis
    n 1: a shrub that is cultivated by Arabs for its leaves which
         are chewed or used to make tea