The Collaborative International Dictionary of English v.0.48:

Intercourse \In"ter*course\, n. [Formerly entercourse, OF.
   entrecours commerce, exchange, F. entrecours a reciprocal
   right on neighboring lands, L. intercursus a running between,
   fr. intercurrere to run between. See Inter-, and Course.]
   1. A commingling; intimate connection or dealings between
      persons or nations, as in common affairs and civilities,
      in correspondence or trade; communication; commerce;
      especially, interchange of thought and feeling;
      association; communion.
      [1913 Webster]

            This sweet intercourse
            Of looks and smiles.                  --Milton.
      [1913 Webster]

   2. Same as sexual intercourse.
      [PJC]

   Sexual intercourse, sexual or carnal connection; coition;
      copulation, especially between humans.

   Syn: Communication; connection; commerce; communion;
        fellowship; familiarity; acquaintance.
        [1913 Webster]

WordNet (r) 3.0 (2006):

sexual intercourse
    n 1: 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, coition, sexual congress, congress, sexual
         relation, relation, carnal knowledge]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "sexual intercourse":
   act of love, adultery, amorous dalliance, aphrodisia, ass, balling,
   billing and cooing, bundling, caressing, carnal knowledge, climax,
   cohabitation, coition, coitus, coitus interruptus, commerce,
   congress, connection, copula, copulation, coupling, cuddling,
   dalliance, diddling, fondling, fornication, hugging, intercourse,
   intimacy, kissing, lollygagging, lovemaking, making it with,
   marital relations, marriage act, mating, meat, necking, nestling,
   nuzzling, onanism, orgasm, ovum, pareunia, petting, procreation,
   relations, screwing, sex, sex act, sexual climax, sexual commerce,
   sexual congress, sexual relations, sexual union, sleeping with,
   snuggling, sperm, spooning, venery