no obj.
1- (of water or food that is being heated) stay just below boiling point while bubbling gently（加热的水或食物）慢慢沸腾：
the goulash was simmering slowly in the oven
菜炖牛肉在炉子上慢慢沸腾
figurative 〈喻〉the disagreement simmered for years and eventually boiled over.
这些年一直意见不合, 最终闹得沸沸扬扬。
1.1
- with obj. keep (something) at such a point when cooking or heating it煨, 炖：
simmer the sauce gently until thickened.
用文火煨调味汁直至变浓。
1.2
- be in a state of suppressed anger or excitement生闷气, 压制兴奋：
she was simmering with resentment.
她强压怨气。
1.3
simmer down
become calmer and quieter息怒; 平静。
in sing.
- a state or temperature just below boiling point即将沸腾状态：
bring the water to a simmer.
让水慢慢沸滚。
词源
mid 17th cent.: alteration of dialect simper (in the same sense)， perhaps imitative.