Source : Webster's Revised Unabridged Dictionary (1913)

Ninety \Nine"ty\, a. [See {Nine}, and cf. {Forty}.]
   Nine times ten; eighty-nine and one more; as, ninety men.

Ninety \Nine"ty\, n.; pl. {Nineties}.
   1. The sum of nine times ten; the number greater by a unit
      than eighty-nine; ninety units or objects.

   2. A symbol representing ninety units, as 90 or xc.

Source : WordNet®

ninety
     adj : being ten more than eighty [syn: {90}, {xc}]

ninety
     n : the cardinal number that is the product of ten and nine
         [syn: {90}, {XC}]