advb. phr. [A prep.1 + SIMMER.] On the simmer, simmering.

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1849.  J. Wilson, in Blackw. Mag., LXV. 767. Dods reports that the Boiler is wroth, the furnace at a red heat, Pots and Pans a-simmer—the Culinary Spirit impatient to be at work.

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