1 concept, conception, construct, thought, notion, plan, design, scheme, suggestion, recommendation:
Is that your idea of a good singing voice? Peter has an excellent idea for increasing sales
2 notion, fancy, impression, picture, (mental) image, concept, conception, perception, understanding, awareness, apprehension, inkling, suspicion, hint, suggestion, approximation, clue, intimation, guess, estimate, estimation, impression:
I haven't the slightest idea what you are talking about. Can you give us any idea of the cause of the delay?
3 belief, opinion, sentiment, feeling, teaching(s), doctrine, tenet, principle, philosophy, view, viewpoint, outlook, notion, conviction, position, stance:
Western and Eastern ideas differ as to the role of women in society.
4 aim, goal, purpose, objective, object, end, point, reason, raison d'être:
What was the idea of telling the teacher? The idea behind the scheme was to boost sales. The idea of the game is to capture your opponent's king
5 hypothesis, theory, notion, dream, fantasy or phantasy:
His invention is based on the idea of an anti-gravity device.