Green’s Dictionary of Slang

1. (US) a beating, fatal or otherwise.

1835		Worcester Herald 26 Dec. 4/3: A sluging [sic], a thrashing, a beating.
1862		C.C. Robinson Dial. Leeds 413: Gi’e him a good slugging lad!
1884		Science IV. 473: Even pugilism would have no charm if it were mere slugging [OED].
1890		A.C. Gunter Miss Nobody of Nowhere 13: The slugging and scrimmaging [...] had been something awful.
1902		J.A. Riis Battle with the Slum 243: Not every gang has a police record of theft and ‘slugging’ beyond the early encounters of the street.
1928		J. Callahan Man’s Grim Justice 110: A gang of officers came down [...] to give me a slugging.
1935		D. Lamson We Who Are About to Die 235: An occasional [...] slugging keeps the suckers in a proper frame of mind.
1949		N. Algren Man with the Golden Arm 164: They’re goin’ to pin the sluggin’ on me.
1958		Mad mag. Jul.–Aug. 31: First Annual Rat Slugging Jubilee City Dump June 6–12.
1959		J. Thompson Getaway in Four Novels (1983) 107: Sluggings are unheard of in El Rey’s dominion.

2. (US) fighting, punching (in a prizefight).

1882

Nat. Police Gaz. (NY) 18 Feb. 2/1: A poetic sporting reporter describes the ‘slugging’ of the champions as [...] a ‘symphony in gore’ .

3. in fig. use, strenuous efforts.

1939		W. Winchell On Broadway 9 Apr. [synd. col.] Father Kernan’s walloping talks are now heard via WHN Thursdays, 10 p.m. Don’t miss his slugging.
1953		‘John Monahan’ [W.R. Burnett] Big Stan 92: I got no real aptitude for this work. No keenness and no intuition. It’s all plain slugging with me.