Source : Webster's Revised Unabridged Dictionary (1913)

Decade \Dec"ade\, n. [F. d['e]cade, L. decas, -adis, fr. Gr. ?,
   fr. de`ka ten. See {Ten}.]
   A group or division of ten; esp., a period of ten years; a
   decennium; as, a decade of years or days; a decade of
   soldiers; the second decade of Livy. [Written also {decad}.]

         During this notable decade of years.     --Gladstone.

Source : WordNet®

decade
     n 1: a period of 10 years [syn: {decennary}, {decennium}]
     2: the cardinal number that is the sum of nine and one; the
        base of the decimal system [syn: {ten}, {10}, {X}, {tenner}]