NOUN (1)

1. temperature just below the boiling point;
- Example: "the stew remained at a simmer for hours"


VERB (1)

1. boil slowly at low temperature;
- Example: "simmer the sauce"
- Example: "simmering water"

The Collaborative International Dictionary of English v.0.48:

Simmer \Sim"mer\, v. i. [imp. & p. p. Simmered; p. pr. & vb.
   n. Simmering.] [Prov. E. also simper; -- an onomatopoetic
   word.]
   To boil gently, or with a gentle hissing; to begin to boil.
   [1913 Webster]

         I simmer as liquor doth on the fire before it beginneth
         to boil.                                 --Palsgrave.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Simmer \Sim"mer\, v. t.
   To cause to boil gently; to cook in liquid heated almost or
   just to the boiling point.
   [1913 Webster]

WordNet (r) 3.0 (2006):

simmer
    n 1: temperature just below the boiling point; "the stew
         remained at a simmer for hours"
    v 1: boil slowly at low temperature; "simmer the sauce";
         "simmering water"

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "simmer":
   bake, barbecue, baste, be in heat, be livid, be pissed, blanch,
   blaze, bloom, blubber, bluster, boil, boil over, braise, brew,
   broil, brown, browned off, bubble, bubble over, bubble up, burble,
   burn, calm down, carry on, chafe, choke, churn, coddle, combust,
   cook, cool it, cool off, curry, devil, distill, do,
   do to perfection, effervesce, ferment, fire, fizz, fizzle, flame,
   flame up, flare, flare up, flicker, flush, foam, fret, fricassee,
   frizz, frizzle, fry, fume, gasp, glow, go on, griddle, grill,
   guggle, gurgle, have a conniption, heat, hiss, incandesce, moil,
   oven-bake, pan, pan-broil, pant, parboil, parch, pissed off, plop,
   poach, prepare, prepare food, radiate heat, rage, raise Cain,
   raise hell, raise the devil, raise the roof, rant, rant and rave,
   rave, roast, saute, scald, scallop, scorch, sear, seethe,
   shimmer with heat, shirr, simmer down, sizzle, smoke, smolder,
   smother, smoulder, spark, sparkle, steam, stew, stifle, stir,
   stir-fry, storm, suffocate, sweat, swelter, take on, throw a fit,
   toast, work