Noun:
1: idea, thought the content of cognition; the main thing you are thinking about; "it was not a good idea"; "the thought never entered my mind"
2: idea a personal view; "he has an idea that we don't like him"
3: approximation, idea, estimation, estimate an approximate calculation of quantity or degree or worth; "an estimate of what it would cost"; "a rough idea how long it would take"
4: mind, idea your intention; what you intend to do; "he had in mind to see his old teacher"; "the idea of the game is to capture all the pieces"
5: musical theme, melodic theme, theme, idea (music) melodic subject of a musical composition; "the theme is announced in the first measures"; "the accompanist picked up the idea and elaborated it"