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.
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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.
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         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"