arbor

[Lat. = a tree.] I. Bot . A tree; that is, a vegetable having branches which are perennial, and are supported upon a trunk; in the latter respect differing from a shrub, one characteristic of which is, that its branches proceed directly from the surface of the ground without having a supporting trunk. (Lindley: Introd. to Bot .) II. Mechanism: 1. The axis or spindle of a machine; as, for instance, of a crane or windmill. 2. That part of a machine which sustains the rest.