Source : Webster's Revised Unabridged Dictionary (1913)

Fifty \Fif"ty\, a. [AS. f[=i]ftig; akin to OHG. finfzug,
   fimfzuc, G. f["u]nfzig, funfzig, Goth. fimftigjus. See
   {Five}, and {Ten}, and cf. {Fifteen}.]
   Five times ten; as, fifty men.

Fifty \Fif"ty\, n.; pl. {Fifties}.
   1. The sum of five tens; fifty units or objects.

   2. A symbol representing fifty units, as 50, or l.

Source : WordNet®

fifty
     n 1: the cardinal number that is the product of ten and five
          [syn: {50}, {L}]
     2: a United States bill worth 50 dollars [syn: {fifty dollar
        bill}]

fifty
     adj : being ten more than forty [syn: {50}, {l}]