Either of the vertical sides of a doorway, arch, window, or other opening. (Dictionary.com)
Either of two stones, timbers, etc., forming the sidepieces for the frame of an opening. (Dictionary.com)
A side post or surface of a doorway, window, or fireplace. (Oxford Dictionaries)
How do I repair a broken wooden door jamb?
Blog about home design. Jamb.
Pocket Door Jamb.