The Collaborative International Dictionary of English v.0.48:

Eighty \Eight"y\, a. [AS. eahtatig, where the ending -tig is
   akin to English ten; cf. G. achtzig. See Eight, and Ten.]
   Eight times ten; fourscore.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Eighty \Eight"y\, n.
   1. The sum of eight times ten; eighty units or objects.
      [1913 Webster]

   2. A symbol representing eighty units, or ten eight times
      repeated, as 80 or lxxx.
      [1913 Webster]

WordNet (r) 3.0 (2006):

eighty
    adj 1: being ten more than seventy [syn: eighty, 80, lxxx,
           fourscore]
    n 1: the cardinal number that is the product of ten and eight
         [syn: eighty, 80, LXXX, fourscore]