The Collaborative International Dictionary of English v.0.48:

Copulate \Cop"u*late\, a. [L. copulatus, p. p. of copulare to
   couple, fr. copula. See Copula.]
   1. Joined; associated; coupled. [Obs.] --Bacon.
      [1913 Webster]

   2. (Gram.) Joining subject and predicate; copulative. --F. A.
      March.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Copulate \Cop"u*late\, v. i. [imp. & p. p. Copulated; p. pr. &
   vb. n. Copulating.]
   To unite in sexual intercourse; to come together in the act
   of generation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

copulate
    v 1: engage in sexual intercourse; "Birds mate in the Spring"
         [syn: copulate, mate, pair, couple]

Moby Thesaurus II by Grady Ward, 1.0:

136 Moby Thesaurus words for "copulate":
   accouple, accumulate, agglutinate, amass, articulate, assemble,
   associate, ball, band, be intimate, beget, bill and coo, bond,
   bracket, breed, breed true, bridge, bridge over, bunch, bunch up,
   cement, chain, clap together, clot, cluster, cohabit, collect,
   combine, come together, commit adultery, comprise, concatenate,
   conglobulate, congregate, conjoin, conjugate, connect, converge,
   couple, cover, crossbreed, crowd, dally, date, diddle, embrace,
   encompass, engender, father, flock together, flow together,
   forgather, fornicate, frig, fuse, gang around, gang up, gather,
   gather around, generate, get, glue, have sex,
   have sexual relations, herd together, hive, horde, huddle, inbreed,
   include, join, knot, lay, lay together, league, lie with, link,
   lollygag, lump together, make it with, make love, make out, marry,
   marshal, mass, mate, meet, merge, mill, mobilize, mother, mount,
   multiply, muster, neck, outbreed, pair, pet, piece together,
   procreate, proliferate, propagate, put together, rally,
   rally around, rendezvous, reproduce in kind, roll into one, screw,
   seethe, serve, service, sire, sleep with, smooch, solder, span,
   splice, spoon, stick together, stream, surge, swarm, sweet-talk,
   take in, tape, throng, tie, toy, trifle, unify, unite, wanton,
   weld, whisper sweet nothings, yoke