fornicate
■ verb formal or humorous have sexual intercourse with someone one is not married to.

fornication noun
fornicator noun

C16 (earlier (ME) as fornication): from eccles. L. fornicat-, fornicari ‘to arch’, from L. fornix, fornic- ‘vaulted chamber’, later ‘brothel’.
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Merriam-Webster Collegiate® Dictionary
for·ni·cate
Pronunciation: ‘fȯr-nə-ˌkāt
Function: verb
Inflected Form: -cat·ed ; -cat·ing
Etymology: Late Latin fornicatus, past participle of fornicare to have intercourse with prostitutes, from Latin fornic-, fornix arch, vault, brothel
Date: 1552

intransitive verb : to commit fornication
transitive verb : to commit fornication with
–for·ni·ca·tor -ˌkā-tər\ noun
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English-Serbian dictionary
Fornicate
Provoditi Blud