Source : Webster's Revised Unabridged Dictionary (1913)

Twenty \Twen"ty\, a. [OE. twenty, AS. tw?ntig, twentig; akin to
   OFris. twintich, OS. tw?ntig, D. & LG. twintig, OHG.
   zweinzug, G. zwanzig, Goth. twai tigjis; that is, two tens.
   See {Twain}, {Two}, and {Ten}.]
   1. One more that nineteen; twice; as, twenty men.

   2. An indefinite number more or less that twenty. --Shak.

            Maximilian, upon twenty respects, could not have
            been the man.                         --Bacon.

Twenty \Twen"ty\, n.; pl. {Twenties}.
   1. The number next following nineteen; the sum of twelve and
      eight, or twice ten; twenty units or objects; a score.

   2. A symbol representing twenty units, as 20, or xx.

Source : WordNet®

twenty
     adj : denoting a quantity consisting of 20 items or units [syn: {20},
            {xx}]

twenty
     n 1: the cardinal number that is the sum of nineteen and one
          [syn: {20}, {XX}]
     2: a United States bill worth 20 dollars [syn: {twenty dollar
        bill}]