brainstorm

Concise Oxford English Dictionary © 2008 Oxford University Press:
brainstorm/ˈbreɪnstɔːm/

▶noun

• 1 Brit. informal a moment in which one is suddenly unable to think clearly.

• 2 a spontaneous group discussion to produce ideas and solutions to problems.

  ■ N. Amer. informal a sudden clever idea.

▶verb (often as noun brainstorming) produce an idea or solution by having a group discussion.