simmer

Etymology 1

From alteration of dialectal simper, from Middle English simperen (“to simmer”), of possibly imitative origin. First attested in the intransitive sense. The noun is from the verb. First attested in the late 15ᵗʰ century.

verb

1. (intransitive) To cook or undergo heating slowly at or below the boiling point.
   The soup simmered on the stove.
   The locomotive was the now inevitable American 2-8-0, No. 2623. There she stood, effectively blocking the level crossing, simmering gently, massively inert. It was almost dark, and one's final sight was of her high, firelit cab, the enginemen nonchalantly leaning out, waiting for the right-away, while impatient road convoys piled up on both sides of the crossing. 1945 January and February, “Notes and News: American Locomotives in France”, in Railway Magazine, page 46
   That way, the heat can circulate under the meat and prevent it from simmering in its juices. 2004, Susan Westmoreland, The Good Housekeeping Cookbook, Hearst Books, page 89
2. (transitive) To cause to cook or to cause to undergo heating slowly at or below the boiling point.
   Simmer the soup for five minutes, then serve.
   There are other easy ways you can bake and simmer and sauté wild game without qualifying as a gourmet cook. 1981, Phyllis Hobson, Easy Game Cookery, Storey Publishing, page 2
3. (intransitive, figurative) To be on the point of breaking out into anger; to be agitated.
   Maybe that really did happen, and Robin's anger at his wife had simmered for this long? 2006, Earl Ganz, The Taos Truth Game, UNM Press
4. (intransitive, figurative) 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.
   I tried to get through to him; all that's left for me to do is simmer.
5. (intransitive, figurative) To develop gradually, of an idea or plan.
   The idea for The Sims was one that had been simmering in Wright's mind for quite some time, and was initially conceived as an architecture simulation. 2003, Mark H. Walker, Games That Sell!, Wordware Publishing, Inc., page 162

noun

1. The state or process of simmering.
   The kettle was kept on the simmer.

Etymology 2

From sim (“simulation”, noun) + -er.

noun

1. (informal, video games) Someone who plays a sim (a simulation game), particularly The Sims.