Green’s Dictionary of Slang

1. the act of complaining, of finding fault.

1639		J. Taylor Crabtree Lectures 76: The Farriers Dyet which he used to expect from his wife when he used to come home late [...] I am sure a Medler, Hartichoake, / A Crab and a small reason.
1893		Field 11 Mar. 347/1: It will be said I am dreadfully ‘on the crab’, but I believe what I have written is only the simple truth.
1919		J. Buchan Mr Standfast (1930) 696: When I first struck them my only crab was that the officers weren’t much better than the men.
1924		John Buchan Three Hostages in Buchan (1930) 870: The crab of the place was its neighbours, it seemed.

2. (UK Und.) a problematic individual.

1843		Bellew Memoirs of a Griffin I 166: The mother of the amiable widow (a nonpareil grafted on a crab).
1846		Swell’s Night Guide 75: Vhy Owen; said Bill you know its no use of me being nuts, ven the donna’s only nut crackers [...] but I know she’s a dead crab to a cove.

3. (US) a nag, a complainer.

1851		Manchester Spy (NH) 20 Sept. n.p.: He’s a sour, cross and crabbed sort of fellow, and they call him Crab Smith.
1914		T.A. Dorgan Indoor Sports 30 Sept. [synd. cartoon] Any old time a fellow begins to talk about what a pip of a dame his wiff is [...] she’s usually a crab.

4. (UK Und.) a problem that emerges during an act of theft.

1865

Leaves from Diary of Celebrated Burglar 32/1: Joe thought it was merely a ‘crab’ the ‘wire’ had caught, and paid no attention to Jack’s getting before him and out of his sight.

5. any form of problem; that which places one at a disadvantage.

1865

Leaves from Diary of Celebrated Burglar 39/2: But if she’s ‘bawled out’ and the ‘sugar blewed,’ that puts a ‘crab’ on the whole of it.