The noun idea has 5 senses (first 5 from tagged texts)
1. (539) 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. (119) idea -- (a personal view; "he has an idea that we don't like him")
3. (58) estimate, estimation, approximation, idea -- (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. (25) 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. (5) theme, melodic theme, musical 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")