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.
an affectionate soubriquet for the person that has woken your heart and dispelled your misgivings about the world at large (re its "shame and terror" -Saroyan).
A person who is into all things motorized. This can be cars, motorcycles, machines, planes, or boats, but specifically relating to the engine and power delivery. Knowing how to weld and machine metal are also traits of a gearhead.
Dude, she's such a gearhead. Go show her that old lathe and tools in your grandfather's garage and she'll be in heaven.