simmer - To heat a liquid, usually a stew or soup, just below the boiling point, allowing it to cook slowly; or to stay in a slow, controlled state of progress or tension, often before a larger event or change occurs.
He was simmering with anger, but he kept it inside and didn't say out loud what he was thinking and feeling.
compliant - Being willing to do what one is asked to do, following set of rules, regulations, and standards.
Though most people don't enjoy paying taxes, they are compliant either because they feel it is right, or because they fear getting caught if they cheat.