In general, a state of heightened activity or concentration. In mechanics, overdrive is a gearing mechanism of a motor vehicle engine that reduces the power output required to maintain driving speed in a specific range by lowering the gear ratio. In audio, overdrive is generally considered to be another word for distortion or clipping. When you overdrive something with too much level it distorts. For guitarists, however, there is a distinction between overdrive and distortion. In the domain of guitar sounds distortion generally means extreme distortion and is associated with a buzzing or “fuzz” type of sound. To guitarists overdrive represents the guitar equivalent of the general or mechanical definition above. It is a state of (for lack of a better term) semi-distortion. A heightened concentration of harmonic energy and presence, but not the same as all out distortion. Technically it is just distortion, but it’s mild enough that more of the character of the guitar comes through.