Having a very powerfully visual trip after taking a hallucinogen. Be it mushrooms, acid, absinthe, etc...
Taken from the SouthPark episode Sexy Action School News, when they go into the pharmacy to buy some cough syrop to 'have some ideas' The pharmacist tells them "if you really want to trip balls" and suggests a certain brand of cough syrop to them. The episode later demonstrates said tripping of balls.
"oh man, I did some beeg, and now I'm trippin' balz!"