To seethe means to be intensely angry while trying to contain it, like a pot of water bubbling just before it boils over. When you seethe, you're furious inside but holding it in, at least for the moment. Your face might turn red, your jaw might clench, and you can feel the anger churning inside you.

Imagine your little brother breaks your favorite model that took you weeks to build, and you stand there seething while your parents talk to him. Or picture a student who studied hard for a test, only to watch a classmate cheat their way to a better score. That hot, boiling feeling of controlled rage is seething.

Just like water seethes and bubbles when heated, anger can make you feel like you're boiling inside. Sometimes people describe a crowd as seething with anger when many people are furious about something.

Seething is different from yelling or throwing a tantrum. When you seethe, the anger stays mostly inside, building pressure. It's that moment before an explosion, when you're working hard to keep your composure even though you're furious.