Green’s Dictionary of Slang

chug v.1

[abbr. chug-a-lug v.]

1. to drink down in a single draught, to drink quickly; thus chugger n., a drinker; (US campus) chugging contest n., a drinking competition in which each contestant has to down a succession of drinks in a single swallow.

[[Aus]Sun. Times (Perth) 10 May 1/1: Even the star of the Thirsty Thirteen couldn’t persuade them [i.e. vaudeville stars the Klos Sisters] to chug-chug [and] a champagne lunch was also foregone].
[US] Frank Zappa ‘The Idiot Bastard Son’ [lyrics] I don’t know but I chugged a fifth of White Port once and passed out one day.
[US](con. 1960s) R. Price Wanderers 34: The guys were getting high, especially Perry, chugging Sevens as fast as he could.
[US]P. Conroy Great Santini (1977) 384: The real warhorse among the contestants drank last; this position of honour was reserved for the best chugger in the squadron.
[US]R. Price Blood Brothers 19: He was chain-smoking and chugging seventy-sevens.
[US]D. Woodrell Muscle for the Wing 46: Bell [...] took a tentative sip of the bourbon, then raised it again and chugged.
[US]D. Hecht Skull Session 181: Damon chugged the beer the barman had set down.
[US]T. Dorsey Hurricane Punch 177: Serge chugged the mug dry.
[US]T. Dorsey Riptide Ultra-Glide 117: Serge uncapped a thermos of coffee and chugged.

2. in fig. use, ‘to swallow’.

[US]B. Hamper Rivethead (1992) 132: You would have half the work force breaking their backs and chugging the work load while the other half were off playing cards.