A bird of the family Cuculidae, noted for brood parasitism

• Especially the common cuckoo with a two-note call

The characteristic two-note call of that bird

The small bird figure that pops from a cuckoo clock

• By extension, a cuckoo clock

A person who installs themselves where they do not belong

A crazy or foolish person

To make the call of a cuckoo

• To repeat something incessantly
• To take over a vulnerable person’s home for criminal use (UK)

Crazy; not sane