The verb to bristle means to react with sudden anger or offense, like a cat whose fur stands up when it feels threatened. When someone bristles at a comment, you can almost see them stiffen and become defensive. A student might bristle when a friend suggests their science project looks rushed, even if the friend meant to be helpful. Your older brother might bristle when you point out he forgot to take out the trash.

The word comes from how animals' hair or fur stands straight up when they're alarmed or angry. A dog's hackles bristle when it senses danger. A porcupine's quills bristle outward as a warning. In humans, we use the word for that same instant reaction: that flash of irritation or pride that makes someone pull back, cross their arms, or snap a quick reply.

As a noun, a bristle is a short, stiff hair or fiber. A hairbrush has bristles. So does a broom or a toothbrush. These bristles stick out stiffly in many directions, which helps you see the connection: when you bristle with anger, you're like those stiff, outward-pointing hairs on a brush, suddenly rigid and defensive, ready to push back against whatever bothered you.