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]