Source : Webster's Revised Unabridged Dictionary (1913)

Four \Four\, n.
   1. The sum of four units; four units or objects.

   2. A symbol representing four units, as 4 or iv.

   3. Four things of the same kind, esp. four horses; as, a
      chariot and four.

   {All fours}. See {All fours}, in the Vocabulary.

Four \Four\, a. [OE. four, fower, feower, AS. fe['o]wer; akin to
   OS. fiwar, D. & G. vier, OHG. fior, Icel. fj?rir, Sw. fyra,
   Dan. fire, Goth. fidw?r, Russ. chetuire, chetvero, W. pedwar,
   L. quatuor, Gr. ?, ?, ?, Skr. catur. ? 302. Cf. {Farthing},
   {Firkin}, {Forty}, {Cater} four, {Quater-cousin}, {Quatuor},
   {Quire} of paper, {tetrarch}.]
   One more than three; twice two.

Source : WordNet®

four
     adj : being one more than three [syn: {4}, {iv}]

four
     n : the cardinal number that is the sum of three and one [syn: {4},
          {IV}, {tetrad}, {quatern}, {quaternion}, {quaternary}, {quaternity},
          {quartet}, {quadruplet}, {foursome}, {Little Joe}]