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

A circulation pattern over Europe is creating "the equivalent of a traffic jam in the atmosphere which locks in heat", Samantha Burgess from the European Centre for Medium-Range Weather Forecasts, told AFP.

From Barron's • Jun. 23, 2026

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

Ground-level ozone, often called “smog,” is a corrosive gas that forms when pollution from vehicles and other sources reacts in heat and sunlight.

From Los Angeles Times • Apr. 22, 2026

I, meanwhile, croaked out a laugh that sounded like a rhinoceros in heat.

From "From Twinkle, with Love" by Sandhya Menon