1. with ref. to liquids.
(a) [late 17C+] (also whet) a (measure of) alcohol, often as take a w(h)et, to have a drink; thus wet stuff, alcohol.
(b) [late 19C–1930s] (US) an anti-Prohibitionist, who wants alcohol to remain legal.
(c) [1920s+] the act of urination.
(d) [1960s] (US campus) a drinking party.
2. [1930s+] (mainly UK juv., also wet end, wetso) an ineffectual, weak, foolish person.
3. see wetback n.
4. (US black / drugs) phencyclidine.
money for the purchase of drink.