Green’s Dictionary of Slang

1. (US) to shoot dead; also fig. use.

1897		A.H. Lewis Wolfville 57: I knows men [...] as would beef him right yere an’ leave him as a companion piece to that compadre of his you downs.
1939		L. Short Raiders of the Rimrock 85: It’s root hog or die now, Lugan! Hell, what’s stoppin’ Sands from havin’ the whole lot of us beefed? [Ibid.] 202: ‘Three jaspers tried to beef me to-night,’ Tim said quietly. ‘I killed two. I’m looking for the third.’.
1947		W.D. Overholser Buckaroo’s Code (1948) 55: When we get the orders [...] we’ll beef every man jack of you.

2. (US) to stab.

1943

R.L. Bellem ‘Dead Man’s Guilt’ Dan Turner – Hollywood Detective May 🌐 There was a sharp, triangular wound in her chest; crimson gravy was leaking out of it in a thin stream. Some dirty disciple had beefed her with a shiv.

3. (orig. US) to knock (someone) down.

1926		J. Black You Can’t Win (2000) 152: Some hard-fisted miner beefed him like an ox with a fast one to the jaw, and kicked his ‘gat’ out into the street.
1931		O. Strange Law O’ The Lariat 76: An’ if he’d beefed yu it would ’a’ served yu right.

4. to engage in sexual intercourse.

1973		(con. mid-1960s) J. Patrick Glasgow Gang Observed 68: She’s a right beefer [...] Only good fur beefin’.
1975		G. Underwood ‘Razorback Sl.’ in AS L:1/2 56: beefvt Engage in sexual intercourse.
1984		Partridge DSUE (8th edn) 64/1: since mid-1940s.