Wiktionary
vb. To drink the entirety of in a short period; ''originally'' and ''especially'', in a single gulp.
Usage examples of "drink off".
Cajeiri dislodged an appetizer reaching for it, and accidentally fired the drink off at a tangent trying to recover the nudged globe.
She maintained one day, in opposition to her husband, that she could drink off a large glass of brandy, and, as Charles was stupid enough to dare her to, she swallowed the brandy to the last drop.
Harking said, pulling his drink off the conveyer as it passed and taking a long swallow.
He snagged a drink off a passing tray and let the familiar taste of the wine soothe him while he contemplated strategy.
He sent him to bed without any fire, taught him to drink off large draughts of rum, and to jeer at religious processions.