Oxford's English Dictionary's definitions

Fireball

To take a hit of marijiuana and then chase it with a swig of hard liquor (specifically Tequila, Burbon, Whiskey or some other such drink). As exemplified by Bill Murray and Chevy Chase in the film Caddyshack.

Chevy: (takes a toke of marijiuana)
Bill: c'mon pal fireball it!
Chevy: (drinks whiskey, coughs uncontrollably)

by Oxford's English Dictionary January 28, 2017