n Any of various birds, of the family Cuculidae (from Latin (term|cuculus||cuckoo|lang=la)), famous for laying its eggs in the nests of other species; but especially the common cuckoo, Cuculus canorus, that has a characteristic two-note call
n The sound of that particular bird.
n The bird shaped figure found in Swiss/German clocks (cuckoo clocks) or the clock itself.
n Someone found where they shouldn't be (used especially in the phrase 'A cuckoo in the nest'.)