Definition of highballs:
(n) :
A cocktail made from a spirit plus soda water etc.
(n) :
(rail transport, US) An all clear or full speed ahead signal.
(n) :
(climbing) A very high bouldering problem, often with a hard landing.
(v) :
To make an estimate which tends toward exaggeration.
(v) :
(US, slang, possibly dated) To move quickly; to hightail.
(n) :
Clipping of highball glass, a tall glass tumbler used for serving highballs. [A tall glass tumbler used for highballs, usually holding 240–350 mL.]