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

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

But they dropped off the pace in the second, clocking 55.04secs - the 12th-quickest time in heat two - to lose four places in the standings before Sunday's medal-deciding heats.

From BBC • Feb. 21, 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

His heart was kicking under his vest like a mule in heat.

From "Song of Solomon" by Toni Morrison