1. A bushing in the hub of a wheel, through which the axle passes.
2. The journal box of a rotating axle, especially a railway axle.
Note: In railway construction, the axle guard, or pedestal, with the superincumbent weight, rests on the top of the box (usually with a spring intervening), and holds it in place by flanges. The box rests upon the journal bearing and key, which intervene between the inner top of the box and the axle.