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

To reach this level of sensitivity, the researchers used a calorimeter, a device designed to measure extremely small changes in heat energy.

From Science Daily • May 21, 2026

Will it end in heat death, expanding into a frozen and lifeless expanse?

From The Wall Street Journal • May 19, 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

If successful, Karman could dent the market share of Trane Technologies and Schneider Electric, the leaders in heat rejection systems.

From Los Angeles Times • Jan. 22, 2026

As the flame grew in heat and height, Nathan added bigger and bigger pieces of wood.

From "Healer of the Water Monster" by Brian Young