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

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

Their times in heat three and four were the sixth and 10th quickest respectively, and a shake of the head from Hall after run three illustrated his disgruntlement at how these Games have gone.

From BBC • Feb. 22, 2026

This achievement confirms that material purity plays a decisive role in heat transfer performance and opens a path toward even more efficient heat-conducting materials.

From Science Daily • Nov. 12, 2025

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

“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