The Collaborative International Dictionary of English v.0.48:

brainstorm \brain"storm`\ n.
   the clear (and often sudden) understanding of a complex
   situation; a sudden brilliant insight.

   Syn: insight, brainwave.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

brainstorm \brain"storm`\ v. t. & i.
   to try to solve a problem by discussing it exhaustively in an
   intense group meeting encouraging uninhibited and spontaneous
   contributions from all members.

   Syn: practice brainstorming.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

brainstorm
    n 1: the clear (and often sudden) understanding of a complex
         situation [syn: insight, brainstorm, brainwave]
    v 1: try to solve a problem by thinking intensely about it