an·i·so·gam·ete 
(ăn-ī′sō-gămēt, ăn′ĭ-)
(ăn-ī′sō-gămēt, ăn′ĭ-)n.
Either of two conjugating gametes that differ in structure or behavior, such as the small motile male spermatozoon and the larger nonmotile female ovum. Also called heterogamete.