bane [ bayn ] (plural banes) noun Definition: 1. something that causes misery: something that continually causes problems or misery It's the bane of my life. 2. something that causes ruin: something that causes death, destruction, or ruin ( literary or archaic ) 3. deadly poison: a fatal poison ( often used in combination in the names of poisonous plants ) [ Old English bana< Germanic] the bane of somebody's existence or life somebody or something that is a constant source of trouble or annoyance