Real Dictionary

cuckoo
countable noun: A cuckoo is a bird that has a call of two quick notes, and lays its eggs in other birds' nests.

cuckoo in American English
any of a family (Cuculidae, order Cuculiformes) of birds with a long, slender body, grayish-brown on top and white below: many, including the European species (Cuculus canorus), lay eggs in the nests of other birds, but the American species hatch and rear
crazy; foolish; silly
to repeat continually, as the cuckoo does its call
to utter or imitate the call of a cuckoo
adjective: irrational; silly; foolish
intransitive verb: to utter the call of the cuckoo or an imitation of it
noun: a common European bird, Cuculus canorus, of the family Cuculidae, noted for its characteristic call and its brood parasitism
transitive verb: to repeat monotonously

cuckoo in British English
adjective: irrational or foolish
exclamation: an imitation or representation of the call of a cuckoo
noun: any bird of the family Cuculidae, having pointed wings, a long tail, and zygodactyl feet: order Cuculiformes. Many species, including the European cuckoo (Cuculus canorus), lay their eggs in the nests of other birds and have a two-note call
verb: to repeat over and over