Green’s Dictionary of Slang

1. to drink, to toast.

1665		Head Eng. Rogue I 37: [We] tipt to each other a Gage of Booz.
c.1698		B.E. Dict. Canting Crew n.p.: Tip it all off, Drink it all off at a Draught.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) II [as cit. c.1698].
1800		‘The Vicar and Moses’ Songster’s Companion 45: Each tipt off a jill, for fear they should chill, And then staggered away.
1822		D. Carey Life in Paris 14: If you prefer, you may tip it / Alone, like your sulky nabob.
2017		R. Friedman Street Warrior 85: The tavern had been around since the Revolutionary War. George Washington was known to have tipped a few there.

2. (US campus) to drink heavily.

1975

G. Underwood ‘Razorback Sl.’ in AS L:1/2 68: I could tell by the way he staggered down the steps he had been tipping.