cuckoo

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A grayish European bird (Cuculus canorus) that has a characteristic two-note call and lays its eggs in the nests of birds of other species.
2. n. Any of various related birds of the family Cuculidae, having grayish-brown plumage and a slender body.
3. n. The call or cry of one of these birds.
4. n. Slang A foolish or crazy person.
5. v. To repeat incessantly, as a cuckoo does its call.
6. adj. Slang Lacking in sense; foolish or crazy.

Century Dictionary and Cyclopedia

1. n. A bird of the family Cuculidœ, and especially of the subfamily Cuculinœ or genus Cuculus: so called from its characteristic note. The common cuckoo of Europe is Cuculus canours, about 14 inches long, with zygodactyl feet, broad rounded tail, curved bill, and ashy plumage varied with black and white. It is notorious for its parasitism, having the habit common to many birds of the family of depositing its eggs in the nests of other birds, chiefly smaller than itself, and causing its young to be reared by the foster-parents—a condition generally entailing the destruction of their own progeny. The remarkable cries which have given the bird imitative names in many languages are the love-notes, uttered only during the mating season. The species of cuckoos are very numerous, and are found in most parts of the world; they are not all parasitic. There are several subfamilies of Cuculidœ, and many genera. (See Cuculidœ.) The American or tree-cuckoos are arboricole, not parasitic, and are confined to America; they are also called hook-billed cuckoos, a term not of special pertinence. The ground-cuckoos are American birds of terrestrial habits. The crested cuckoos are old-world forms, as are also the coucals, lark-heeled or spur-heeled cuckoos, also called pheasant-cuckoos.
2. n. A simpleton; a fool: used in jest or contempt, like the ultimately related gowk.

Wiktionary

1. adj. Crazy; not sane.
2. n. Any of various birds, of the family Cuculidae (from Latin cuculus ("cuckoo")), 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
3. n. The sound of that particular bird.
4. n. The bird shaped figure found in Swiss/German clocks (cuckoo clocks) or the clock itself.
5. n. Someone found where they shouldn't be (used especially in the phrase 'A cuckoo in the nest'.)
6. n. Someone who is crazy.
7. v. To make the call of a cuckoo
8. v. To repeat something incessantly

GNU Webster's 1913

1. n. (Zoöl.) A bird belonging to Cuculus, Coccyzus, and several allied genera, of many species.

WordNet 3.0

1. n. any of numerous European and North American birds having pointed wings and a long tail
2. v. repeat monotonously, like a cuckoo repeats his call
3. n. a man who is a stupid incompetent fool