To have a tendency to want or to be interested in mechanical things; to understand, and be able to work on things of a mechanical nature, or things with gears.
That boy over at AutoZone is a total gearhead, he loves to work on his car.
A term that Ignorant people use to describe others.
People of this sort are calling each other a type of wrench, that moves in a ratcheting motion, It is not a name to call someone, it is a tool often used to work on things with nuts and bolts!
The mechanicused the ratchet to remove the oil drain plug from the automobile.