When water roils, it churns and swirls in a turbulent, disturbed way. Picture a river after a storm, its surface broken by eddies and whirlpools, or a pot of boiling water bubbling violently. The word captures that angry, unsettled movement.

The word also describes emotional turmoil. When something roils your feelings, it stirs up confusion, anger, or anxiety that won't settle down. A shocking announcement might roil a classroom. Rumors can roil a community. After an argument, your thoughts might roil around in your head, making it hard to think clearly or fall asleep.

Roil is stronger than “disturb” or “upset.” When a scandal roils a government or controversy roils a school board meeting, things are in genuine upheaval.

The word sounds like what it describes. Say it out loud and you can almost hear the churning, bubbling chaos it names.