any of numerous European and North American birds having pointed wings and a long tail
"The cuckoo darted through the tall grass, its sharp wingbeats echoing as it chased after the field mice."
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 old woodpecker was frantic when he discovered a bright blue egg nestled deep within his nest from an unsuspecting cuckoo."
repeat monotonously, like a cuckoo repeats his call
"The broken clock on the wall ticked cuckoo every hour on the hour."
To make the call of a cuckoo.
"The old man would sit on his porch and cuckoo all afternoon to mimic the bird's distinctive cry."
Crazy; not sane.
"After spending three hours trying to untangle his own shoelaces, everyone agreed that my neighbor was completely cuckoo."
The word cuckoo likely comes from Old French cocu or coquu, which were probably onomatopoeic imitations of the male Common Cuckoo's song. While earlier English words for the bird existed, the current usage may have been influenced by the bird's habit of laying eggs in other birds' nests.