What does giving a girl a motorboat mean

Giving a girl a motorboat, or going motorboating, is a slang expression for placing one's face against a woman's chest, in her cleavage, and then rapidly rocking one's face from side to side with loose lips while making a humming sound similar to the sound the engine of a motorboat might make.

Motorboating without the consent of the woman would be a criminal offense defined as battery, or unlawful physical contact (not to be confused with assault which is the apprehension of unlawful physical contact), which could result in one being arrested.

During the 2012 CMA awards, host Brad Paisley joked that the band Little Big Town explained to him, backstage, what motorboating was, and acted very surprised.