The figure inclosed by lines through the points contact of the wheels of a vehicle, etc., with the surface or rails on which they run; more esp., the length of this figure between the points of contact of the two extreme wheels on either side.
noun The distance between the front and back wheels of any vehicle with two axles. In skateboarding this is measured between the two sets of inner-most truck holes. (the rear set of the front truck and the front set of the back truck).
The distance between the centers of the front and rear wheels. Measuring and comparing the wheelbase on both sides of a vehicle can identify rear axle misalignment or front wheel setback.