The Collaborative International Dictionary of English v.0.48:

Two \Two\, n.
   1. The sum of one and one; the number next greater than one,
      and next less than three; two units or objects.
      [1913 Webster]

   2. A symbol representing two units, as 2, II., or ii.
      [1913 Webster]

   In two, asunder; into two parts; in halves; in twain; as,
      cut in two.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Two \Two\ (t[=oo]), a. [OE. two, twa, properly fem. & neut.,
   twei, twein, tweien, properly masc. (whence E. twain), AS.
   tw[=a], fem. & neut., tw[=e]gen, masc., t[=u], neut.; akin to
   OFries. tw[=e]ne, masc., tw[=a], fem. & neut., OS. tw[=e]ne,
   masc., tw[=a], fem., tw[=e], neut., D. twee, OHG. zw[=e]ne,
   zw[=o], zwei, G. zwei, Icel. tveir, tv[ae]r, tvau, Sw.
   tv[*a], Dan. to, Goth. twai, tw[=o]s, twa; Lith. du, Russ.
   dva, Ir. & Gael. da, W. dau, dwy, L. duo, Gr. dy`o, Skr. dva.
   [root]300. Cf. Balance, Barouche, Between, Bi-,
   Combine, Deuce two in cards, Double, Doubt, Dozen,
   Dual, Duet, Dyad, Twain, Twelve, Twenty, Twice,
   Twilight, Twig, Twine, n., Twist.]
   One and one; twice one. "Two great lights." --Gen. i. 16.
   "Two black clouds." --Milton.
   [1913 Webster]

   Note: Two is often joined with other words, forming compounds
         signifying divided into, consisting of, or having, two
         parts, divisions, organs, or the like; as two-bladed,
         two-celled, two-eared, two-flowered, twohand,
         two-headed, two-horse, two-leafed or two-leaved,
         two-legged, two-lobed, two-masted, two-named, two-part,
         two-petaled, two-pronged, two-seeded, two-sided,
         two-story, two-stringed, two-toothed, two-valved,
         two-winged, and the like.
         [1913 Webster]

   One or two, a phrase often used indefinitely for a small
      number.
      [1913 Webster]

WordNet (r) 3.0 (2006):

two
    adj 1: being one more than one; "he received two messages" [syn:
           two, 2, ii]
    n 1: the cardinal number that is the sum of one and one or a
         numeral representing this number [syn: two, 2, II,
         deuce]
    2: one of the four playing cards in a deck that have two spots
       [syn: deuce, two]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "two":
   biform, bifurcated, bilateral, bipartisan, bipartite, both, brace,
   couple, couplet, dichotomous, distich, double, double harness,
   doublet, duad, duadic, dual, dualistic, duet, duo, duplex,
   duplicated, dyad, dyadic, identical, match, matched, mates, pair,
   set of two, span, team, the two, twain, twin, twinned, two-sided,
   twosome, yoke