a clock with a small toy figure of a cuckoo in it, which pops out at regular intervals, usually on the hour, to the accompaniment of a sound imitating the bird's call
See cuckoo clock in American Heritage Dictionary 4
cuckoo clock
noun
A wall or shelf clock that announces intervals of time with a sound imitative of a cuckoo's call and often with the simultaneous emergence of a mechanical bird from a small door.