When two animals or people have sexual intercourse to reproduce.
From Latin 'copulare' (to join together or couple), from 'copula' (a bond or link). The word is clinical and scientific rather than crude or vulgar.
This word comes from 'copula,' the same root that gives us 'couple'—so it literally just means 'to join together,' which is why scientists use it as neutral terminology for reproduction!
Complete word intelligence in one call. Free tier — 50 lookups/day.