to cook or cook in a liquid at or just below the boiling point.

to make a gentle murmuring sound, as liquids cooking just below the boiling point.

to be in a state of subdued or restrained activity, development, excitement, anger, etc.

The town simmered with rumors.

to keep (liquid) in a state approaching boiling.

to cook in a liquid that is kept at or just below the boiling point.

the state or process of simmering. ?

simmer down,

to reduce in volume by simmering.

Slang . to become calm or quiet, as from a state of anger or turmoil

We waited for the audience to simmer down.

verb

simmer