Any of various birds, of the family Cuculidae, 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.
The sound of that particular bird.
The bird shaped figure found in Swiss/German clocks (cuckoo clocks) or the clock itself.
Someone found where they shouldn't be (used especially in the phrase a cuckoo in the nest).
