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.
   [1913 Webster]

         Cold congregates all bodies.             --Coleridge.
   [1913 Webster]

         The great receptacle
         Of congregated waters he called Seas.    --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

congregating
    n 1: the act of congregating [syn: congregation,
         congregating]