To cook or undergo heating slowly at or below the boiling point.
Example: "The soup simmered on the stove."
To cause to cook or to cause to undergo heating slowly at or below the boiling point.
Example: "Simmer the soup for five minutes, then serve."
To be on the point of breaking out into anger; to be agitated.
To 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.
Example: "I tried to get through to him; all that's left for me to do is simmer."