As a Noun: 1. Behaviour which is not at all sensible. English = stupidity. 2. The quality of being stupid. English = stupidity. 3. The quality of being very stupid. English = idiocy. As a Verb or Adjective: 1. To show a lack of good judgement or intelligence and to be not at all sensible. English = (be) stupid, (be) foolish. 2. To be very stupid. English = (be) idiotic. 3. To be very stupid, silly, unreasonable, inappropriate or ridiculous. English = (be) absurd. Interactive: 1. Used alone to mean that you think that you do not like something and that it annoys you. English = 'How stupid!', 'That's ridiculous!' 2. Used alone to express irritation with yourself for having done something that is foolish or a mistake. English = 'Oops!'