Jamb

Webster's Dictionary of the English Language

·vt ·see Jam, ·vt.

II. Jamb ·noun Any thick mass of rock which prevents miners from following the lode or vein.

III. Jamb ·noun 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.