cuckoo

Any of various birds, of the family Cuculidae within the order Cuculiformes, 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.

(slang) Someone who is crazy.

A person who inveigles themselves into a place where they should not be (used especially in the phrase a cuckoo in the nest).

The sound of that particular bird.

The cuckoo clock itself.

The bird-shaped figure found in cuckoo clocks.

To make the call of a cuckoo.

(UK) To take over the home of a vulnerable person for the purposes of carrying out organized crime in a concealed way.

To repeat something incessantly.

(slang) Crazy; not sane.