Mad, crazy, silly.
The buttocks or anus.
A homosexual man.
Crazy; not sane.
The cuckoo clock itself.
The sound of that particular bird.
A person who inveigles themselves into a place where they should not be (used especially in the phrase a cuckoo in the nest).
Someone who is crazy.
Any of various birds, of the family Cuculidae, famous for laying its eggs in the nests of other species; but especially a common cuckoo (Cuculus canorus), that has a characteristic two-note call.
The bird-shaped figure found in cuckoo clocks.
To make the call of a cuckoo.
To repeat something incessantly.