non-consensual adj.

a prefix used freely in English and meaning "not, lack of," or "sham," giving a negative sense to any word, 14c., from Anglo-French noun-, from Old French non-, from Latin non "not, by no means, not at all, not a," from Old Latin noenum "not one" (*ne oinom, from PIE root *ne- "not" + PIE root *oi-no- "one, unique"). In some cases perhaps from Middle English non "not" (adj.), from Old English nan (see not). "It differs from un- in that it denotes mere negation or absence of the thing or quality, while un- often denotes the opposite of the thing or quality" [Century Dictionary].

1754, "having to do with consent, formed by consent, depending upon consent," from stem of Latin consensus "agreement, accord" (past participle of consentire; see consent (v.)) + -al (1).

Until modern times used almost exclusively with reference to legal contracts and to the eyes working together reflexively; its sense was extended in the language of sociology and psychology from 1950s (of social groups, non-arranged marriages, etc.) and in the legal discussions of rape and other sex crimes by 1977.