As a Noun: 1. An idea which is good, reasonable or appropriate. As a Verb or Adjective: 1. Of an idea, to be well thought out, clear, appropriate. English = (be) sensible, (be) reasonable. 2. To make decisions and judgements that are based on reason rather than on emotion. English = (be) rational. Interactive: 1. Used alone in response to what someone has said or suggested to mean you think their idea is good, reasonable, appropriate or timely. English = 'What a good idea!', 'Now, that's a great idea!' and so on. As Modifier: 1. Used to introduce a sentence in which you express an idea you have, when you think that idea is very good, reasonable, appropriate or timely. English = 'I've got this great idea!', 'Hey! Why don't we...', 'Say, let's...' and so on. 2. Used to repeat someone else's suggestion favourably (ie, when you think it is a good idea too). English = 'That's a great idea....', 'What an idea!....'