2.verbTo cook or undergo heating slowly at or below the boiling point.
"The soup simmered on the stove."
3.verbTo cause to cook or to cause to undergo heating slowly at or below the boiling point.
"Simmer the soup for five minutes, then serve."
4.verbTo be on the point of breaking out into anger; to be agitated.
5.verbTo remain angry with someone or something past the point of exhaustion; to resign oneself to holding a grudge, especially after some failed attempts to resolve a situation.
"I tried to get through to him; all that's left for me to do is simmer."