(1):

(n.) The cutting tool of an engraver on metal, used in line engraving. It is made of tempered steel, one end being ground off obliquely so as to produce a sharp point, and the other end inserted in a handle; a graver; also, the similarly shaped tool used by workers in marble.

(2):

(n.) The manner or style of execution of an engraver; as, a soft burin; a brilliant burin.