In general, that which is set off, from, before, or against, something; as:
1. (Science: botany) A short prostrate shoot, which takes root and produces a tuft of leaves, etc.
2. A sum, account, or value set off against another sum or account, as an equivalent; hence, anything which is given in exchange or retaliation; a set-off.
3. A spur from a range of hills or mountains.
4. A horizontal ledge on the face of a wall, formed by a diminution of its thickness, or by the weathering or upper surface of a part built out from it; called also set-off.
5. A short distance measured at right angles from a line actually run to some point in an irregular boundary, or to some object.
6. (Science: mechanics) An abrupt bend in an object, as a rod, by which one part is turned aside out of line, but nearly parallel, with the rest; the part thus bent aside.
7. A more or less distinct transfer of a printed page or picture to the opposite page, when the pages are pressed together before the ink is dry or when it is poor. Offset staff, a rod, usually ten links long, used in measuring offsets.
Origin: Off – set. Cf. Set-off.
Source: Websters Dictiona