The sexual act of grasping an erect penis and moving it about in a way that you would a car's gearstick, while at the same time, imitating the sound of the gears changing.
Mark was happily receiving a hearty blowjob from the girl from Perth but was caught off guard when she abruptly stopped and began to gearstick him. He noticed that she was particularly adept at imitating the sound of the gears shifting. Perhaps, he thought, she had a passion for car racing.
A person with a thin, long semi-box head, with the upper part being 2/3 wider than the lower half. It is imperative that the head is long but with a rounded top.
Whilst driving down the moterway / freeway. Have your girlfriend give you a blowjob. When she is getting comfortable, accelerate into the back of a lorry.