n. 25B6; verb
the soup was simmering on the stove : BOIL GENTLY, cook gently, bubble.
she was simmering with resentment : BE FURIOUS, be enraged, be angry, be incensed, be infuriated, seethe, fume, smoulder; informal be steamed up, be hot under the collar.
25A0; simmer down BECOME LESS ANGRY, cool off/down, be placated, control oneself, become calmer, calm down, become quieter, quieten down.