Jamb (?), n. [Prov. E. jaumb, jaum, F. jambe a leg, jambe de force a principal rafter. See Gambol.]
1. (Arch) The vertical side of any opening, as a door or fireplace; hence, less properly, any narrow vertical surface of wall, as the of a chimney-breast or of a pier, as distinguished from its face. Gwilt.
2. (Mining) Any thick mass of rock which prevents miners from following the lode or vein.