Smart' and 'intelligent' have the same meaning, but 'smart' is less formal; 'smart' also means 'well-dressed'. 'Clever' is 'mentally quick and resourceful', but can also sometimes be used synonymously with the other two. My son is smart/intelligent. There may be intelligent life on Mars. I ain't so smart, no how. Chimpanzees are intelligent animals. Crows are clever/intelligent/smart birds. Foxes are reputed to be clever. I found a clever solution to our dilemma. .