1) Backcross 2) Bonk 3) Deflower 4) Eff 5) Sodomise 6) Sodomize 1) Conjoin 2) Couple 3) Do it 4) Engage in sexual intercourse 5) Join 6) Make love 7) Mate 8) Pair 
• (a.) Joined; associated; coupled. • (v. i.) To unite in sexual intercourse; to come together in the act of generation. • (a.) Joining subject and predicate; copulative.
Cop'u·late adjective [ Latin copulatus , past participle of copulare to couple, from copula . See Copula .] 1. Joined; associated; coupled. [ Obsolete] Bacon. 2. (Gram.) Joining subject and predicate; copulative. F. A. March. Cop'u·late intransitive verb [ imperfect & past participle Copulated ; present participle & verbal noun Copulating .] To unite in sexual intercourse; to come together in the act of generation. 
[v] - make love
mate verb make love; `Birds mate in the Spring`