The Collaborative International Dictionary of English v.0.48:

Gamete \Gam"ete\ (g[a^]m"[=e]t; g[.a]*m[=e]t"; the latter
   usually in compounds), n. [Gr. gameth` wife, or game`ths
   husband, fr. gamei^n to marry.] (Biol.)
   A sexual cell or germ cell having a single set of unpaired
   chromosomes; a conjugating cell which unites with another of
   like or unlike character to form a new individual. In Bot.,
   gamete designates esp. the similar sex cells of the lower
   thallophytes which unite by conjugation, forming a zygospore.
   The gametes of higher plants are of two sorts, sperm (male)
   and egg (female); their union is called fertilization, and
   the resulting zygote an oospore. In Zool., gamete is most
   commonly used of the sexual cells of certain Protozoa, though
   also extended to the germ cells of higher forms.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

gamete
    n 1: a mature sexual reproductive cell having a single set of
         unpaired chromosomes