Definition of sexes:
(n) :
(uncountable) Sexual activity, usually sexual intercourse unless preceded by a modifier.
(v) :
(chiefly US, colloquial, intransitive) To have sex.
(v) :
(chiefly US, colloquial, transitive) To have sex with.
(n) :
(countable) A category into which sexually-reproducing organisms are divided on the basis of their reproductive roles in their species; the system of such categories, which can differ by organism or by taxonomic branch.
(n) :
(countable) Another category, especially of humans and especially based on sexuality or gender roles.
(n) :
(uncountable) The distinction and relation between these categories, especially in humans; gender.