"Chip on one's shoulder" is an idiom that means to be easily provoked or prone to take offense. Some synonyms for this term include having a "chip on your shoulder," carrying a grudge, feeling resentful, being touchy or prickly, having a short fuse, being easily agitated, and holding a perceived slight against someone. The origin of this phrase is said to come from the practice of putting a chip of wood on one's shoulder and daring others to knock it off, to invite confrontation. When we use this idiom, we imply that someone may be looking for a fight or that they feel attacked or inferior in some way, leading them to overreact or become overly defensive.