According to thesaurus.com :

Main Entry: brainstorm
Part of Speech: verb
Definition: problem-solve
Synonyms: analyze, conceive, conceptualize, conjure up, create, deliberate, dream up, invent, plan, ponder, put heads together, rack brains, share ideas, think

According to thesaladyears.com :

Main Entry: brainstorm
Part of Speech: verb
Definition: problem-solve
Synonyms: gangbang