The Collaborative International Dictionary of English v.0.48:

Six \Six\, n.
   1. The number greater by a unit than five; the sum of three
      and three; six units or objects.
      [1913 Webster]

   2. A symbol representing six units, as 6, vi., or VI.
      [1913 Webster]

   To be at six and seven or To be at sixes and sevens,
      (a) to be in disorder. --Bacon. --Shak. --Swift.
      (b) to be in a dispute or disagreement; -- often used with
          with.
          [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Six \Six\, a. [AS. six, seox, siex; akin to OFries. sex, D. zes,
   OS. & OHG. sehs, G. sechs, Icel., Sw., & Dan. sex, Goth.
   sa['i]hs, Lith. szeszi, Russ. sheste, Gael. & Ir. se, W.
   chwech, L. sex, Gr. ??, Per. shesh, Skr. shash. [root]304.
   Cf. Hexagon, Hexameter, Samite, Senary, Sextant,
   Sice.]
   One more than five; twice three; as, six yards.
   [1913 Webster]

   Six Nations (Ethnol.), a confederation of North American
      Indians formed by the union of the Tuscaroras and the Five
      Nations.

   Six points circle. (Geom.) See Nine points circle, under
      Nine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

six
    adj 1: denoting a quantity consisting of six items or units
           [syn: six, 6, vi, half dozen, half-dozen]
    n 1: the cardinal number that is the sum of five and one [syn:
         six, 6, VI, sixer, sise, Captain Hicks, half a
         dozen, sextet, sestet, sextuplet, hexad]
    2: a playing card or domino or die whose upward face shows six
       pips [syn: six-spot, six]