cheer up verb 2exclamation 1forms 3 verb2 •To become happier or less downcast.I cheered up after seeing the results. •To make someone happier or less downcast.The arrival of the unexpected letter cheered him up almost immediately. exclamation1 •An encouragement to somebody who seems unhappy.Cheer up! Things could be worse. formscheered up · cheering up · cheers up