Green’s Dictionary of Slang

ploughed adj.

drunk.

1853		Dickens ‘Slang’ in Household Words 24 Sept. 75/2: For the one word drunk [...] on the ran-tan, on the re-raw, groggy, ploughed, cut, and in his cups.
1857		‘Ducange Anglicus’ Vulgar Tongue.
1864		London Standard 13 Dec. 3/3: A higher more intense state of beastliness [...] Out [...] Ploughed [...] Top Heavy.
1873		Sl. Dict.
1933		‘William Juniper’ True Drunkard’s Delight.
1955		W. White ‘Wayne University Sl.’ AS XXX:4 303: ploughed; schnockered; way up, adj. Drunk.
1960		G. Swarthout Where the Boys Are 25: I drink. I didn’t in high school because getting plowed then was not so much alcohol as the will to get plowed, which bored me.
1961		H. Ellison Rockabilly (1963) 67: He was ploughed out of his mind.
1974		(con. 1960s) R. Price Wanderers 141: ‘It gets better the more you drink,’ said Joey [...] After a while everyone was plowed.
1989		P. Munro Sl. U. 149: plowed drunk, intoxicated.
1996		Eble Sl. and Sociability 45: Among the synonyms for drunk are [...] messed up, obliterated, ploughed.
2000		G. Pelecanos Shame the Devil 257: The Spot’s drinkers were working people and cops who got plowed early and made their way home.