in heat

Idioms  

1. In a state of sexual excitement immediately preceding ovulation. For example, Our cat's in heat so we have to keep her inside. This expression applies to most female mammals and indicates the period when the animal is fertile and most receptive to mating. [Mid-1700s]

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Example Sentences

For a mass market in heat pumps to take off, electricity can be more expensive than gas, but not that much more expensive.

From BBC • Mar. 22, 2026

Unlike internal combustion engines, which require a large temperature gap to operate efficiently, Stirling engines can run on much smaller differences in heat.

From Science Daily • Feb. 27, 2026

An extra layer of low-moisture cheese between dough and sauce helps lock in heat for travel.

From The Wall Street Journal • Oct. 8, 2025

"If you're working in heat and your body temperature increases by, over a longer period, over 38C, then you are at risk of severe heat-related stress and stroke, kidney failure, dehydration."

From BBC • Aug. 22, 2025

“Her mom invented this recyclable paper coffee cup that holds in heat but keeps the outside from burning your hand.”

From "We Are the Ants" by Shaun David Hutchinson