What does conk mean?
Conk is an informal English word with two main grammatical lives: a verb and a noun. As a verb, it means to hit someone or something squarely on the head, usually in a comic or casual context — a low-hanging branch might conk you as you walk past. Its most familiar form, however, is the phrase "conk out," which describes a machine, engine, or electronic device failing abruptly, or a person collapsing into sleep from sheer exhaustion. As a noun, a conk can mean a blow on the head, though this use is now less common than the verb; separately, in forestry and mycology, "conk" names the hard, shelf-like fruiting body of a wood-rotting fungus that protrudes from tree trunks. The word's tone is light and conversational, making it well suited to informal speech and writing. It should generally be avoided in formal contexts, where plainer terms such as "strike," "fail," or "bracket fungus" would be preferred.
To hit someone or something on the head; (in "conk out") to stop working suddenly, or to fall asleep from exhaustion.
"She was nearly conked on the head by a falling apple."
Almost always used informally; "conk out" applies both to mechanical failure and to people dropping off to sleep.
A blow on the head; also, a hard shelf-like fungal growth projecting from a tree trunk.
"He took a nasty conk on the head during the rugby match."
The head-blow sense is dated and informal; the fungal sense is standard in forestry terminology.
Used chiefly when referring to multiple fungal growths on trees; the head-blow sense is rarely pluralized.
"The old oak was covered in woody conks along its dead lower limbs."
"Conk out" is one of those rare phrases that works equally well for an exhausted engine, a dying laptop battery, and a person who falls asleep mid-sentence.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of conk
Conk first appeared in American English in the nineteenth century as an informal term for a blow on the head, though its ultimate origin is uncertain. The phrase "conk out" developed in the early twentieth century, originally describing aircraft engines cutting out before spreading to machines and people generally. Some dictionaries have suggested a possible link to "conch," but the connection has not been firmly established. The fungal sense arose independently within forestry vocabulary, named after the shape of these bracket fungi.
How conk is actually used
Conk is informal throughout its main uses; the phrase "conk out" is very common in everyday speech for machines breaking down or people dropping off to sleep. The fungal sense of the noun is technical rather than colloquial, used mainly by foresters and mycologists. The verb sense of hitting someone on the head is playful or comic in register rather than serious.
Easily confused with conk
Bonk means much the same thing as conk in the sense of hitting someone on the head, but it also carries a British slang meaning for sexual intercourse that conk does not.