The Collaborative International Dictionary of English v.0.48:

Congregate \Con"gre*gate\, a. [L. congregatus, p. p. of
   congregare to congregate; on- + gregare to collect into a
   flock, fr. grex flock, herd. See Gregarious.]
   Collected; compact; close. [R.] --Bacon.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Congregate \Con"gre*gate\, v. t. [imp. & p. p. Congregated; p.
   pr. & vb. n. Congregating]
   To collect into an assembly or assemblage; to assemble; to
   bring into one place, or into a united body; to gather
   together; to mass; to compact.
   [1913 Webster]

         Any multitude of Christian men congregated may be
         termed by the name of a church.          --Hooker.
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         Cold congregates all bodies.             --Coleridge.
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         The great receptacle
         Of congregated waters he called Seas.    --Milton.
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The Collaborative International Dictionary of English v.0.48:

Congregate \Con"gre*gate\, v. i.
   To come together; to assemble; to meet.
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         Even there where merchants most do congregate. --Shak.
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WordNet (r) 3.0 (2006):

congregate
    v 1: come together, usually for a purpose; "The crowds
         congregated in front of the Vatican on Christmas Eve"

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "congregate":
   assemble, bunch, bunch up, clot, cluster, collect, come together,
   congress, converge, copulate, couple, crowd, date, flock together,
   flow together, forgather, fuse, gang around, gang up, gather,
   gather around, herd together, hive, horde, huddle, league, link,
   mass, meet, merge, mill, muster, raise, rally, rally around,
   rendezvous, seethe, stream, surge, swarm, teem, throng, unite