-An improper form of performing a hand-job
-When a girl, rather than stroking guy's junk properly, thinks it is necessary to pull a guy's penis back and forth like a manual car's gear shifter
Mike: Hey man, how was she?
Dominique: She did it again.
Mike: HA! You got gear shifted!
Mike: Dom, how was it with that girl last night?
Dominique: Dude what the fuck, she gave me the gear shifter.
When a girl is giving a handjob
she thinks it it necessary to pull guy's penis forward and backward similar to that of a car's manual transmission. Also can simply refer to a bad handjob.
Bob: I hooked up with that girl last night
Bill: Was it good?
Bob: No... I got the Gear shifter