What does sandbagging means in drag racing?

Answer 1

It means that a driver gets way ahead of the other car, and lets off of the throttle before the finish line, thus running a slower time, than capable. The advantage is a quicker car, racing a slower one.

Answer 2

A league or tournament bowler who intentionally bowls lower than their capabilities for purposes of loosing or lowering their average is considered sandbagging or called a sandbagger.