What does crab mean?
A crab is a crustacean characterized by a broad, flattened body covered by a hard shell, five pairs of legs, and two front claws used for defense and handling food. Crabs inhabit oceans worldwide and some fresh waters, and they are prized as food across many cuisines, from soft-shell blue crabs to Alaskan king crab. Beyond the animal, 'crab' also refers to its edible flesh, and informally it describes a person who complains constantly or is ill-tempered — hence the adjective 'crabby.' As a verb, 'crab' means to grumble, or in aviation and boating, to move sideways into wind or current. The word carries both neutral culinary connotations and mildly negative social ones, making it versatile in everyday speech.
A crustacean with a broad flat shell, five pairs of legs including two pincers; also its flesh as food.
"She ordered a whole steamed crab at the seafood restaurant."
When referring to the food, 'crab' is typically uncountable ('a bowl of crab').
To complain peevishly; or, in aviation/nautical contexts, to move sideways against wind or current.
"He was always crabbing about his job."
The complaining sense is informal and somewhat dated.
Regular plural. Used when referring to multiple animals; uncountable when referring to flesh as food.
"The tide pools were teeming with small hermit crabs."
Crabs walk sideways because of how their knees bend — and 'crabby' meaning irritable may come from the animal's pinched, defensive posture.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of crab
The word 'crab' derives from Old English 'crabba,' related to Old Norse 'krabbi' and cognate with Dutch 'krab' and German 'Krabs(e),' all tracing back to Proto-Germanic roots associated with scratching or clawing. It has been used in English since before the 12th century to refer to the crustacean. The verb sense meaning 'to complain' appeared later, likely influenced by associations with sourness (as in 'crab apples') and the creature's aggressive posture. Related words include 'crabby,' meaning irritable, which emerged from these same figurative extensions.
Related word forms
How crab is actually used
'Crab' as a noun referring to the animal and its meat is standard in all registers. The verb sense meaning 'to complain' is chiefly informal and somewhat dated, more common in British English. 'Crabby' as an adjective meaning irritable is common and informal. The nautical/aviation sense 'to crab' (move sideways) is technical jargon.
Easily confused with crab
A crawfish is a freshwater crustacean resembling a small lobster with elongated claws, whereas a crab has a broad flat body and short legs.