Meaning of big idea

big' ide'a

Pronunciation: [key]
— Informal. Informal.
  1. any plan or proposal that is grandiose, impractical, and usually unsolicited: You're always coming around here with your big ideas.
  2. purpose; intention; aim: What's the big idea of shouting at me?
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.