sexual union is a noun meaning "the act of pairing a male and female for reproductive purposes". It carries one recorded sense.
the act of pairing a male and female for reproductive purposes
“the casual couplings of adolescents”
“the mating of some species occurs only in the spring”
Definitions, synonyms and semantic relations for sexual union come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.