1) To hollow out. 2) The hollow part in a tube, pipe, or barrel. In optics a central hole running the length of a waveguide or laser tube.
O.E. borian "to bore," from bor "auger," from P.Gmc. *boron, from PIE base *bhor-/*bhr- "to cut with a sharp point" (cf. Gk. pharao "I plow," L. forare "to bore, pierce," O.C.E. barjo "to strike, fight," Alb. brime "hole"). The meaning "diameter of a tube" is first recorded 1572.