Source : Webster's Revised Unabridged Dictionary (1913)

Coition \Co*i"tion\, n. [L. coitio, fr. coire to come together;
   co- + ire to go.]
   A coming together; sexual intercourse; copulation. --Grew.

Source : WordNet®

coition
     n : the act of sexual procreation between a man and a woman; the
         man's penis is inserted into the woman's vagina and
         excited until orgasm and ejaculation occur [syn: {sexual
         intercourse}, {intercourse}, {sex act}, {copulation}, {coitus},
          {sexual congress}, {congress}, {sexual relation}, {relation},
          {carnal knowledge}]