supposesupposesupposessupposedsupposingverb (supposes, supposing, supposed)1to think that something is probably true or will probably happen: ‘Where's Jenny?’ ‘I don't know – I suppose she's still at work.’2a word that you use when you agree with something but are not happy about it: ‘Can I borrow your pen?’ ‘Yes, I suppose so – but don't lose it.’be supposed to1If you are supposed to do something, you should do it: They were supposed to meet us here. You're not supposed to smoke in this room.2(informal) If something is supposed to be true, people say it is true: This is supposed to be a good restaurant.