CUTTHROAT is a Technique a Rogue gets on the 15th level in SLASH'EM.
If you are wielding a bladed weapon, you will have a rn2(5)<TECHLEVEL/10+1 chance, target is killed. Otherwise, MONHP is reduced by MONHP/2+TECHLEVEL.
If the monster is headless, or you are swallowed, you only do TECHLEVEL damage.