estrus

Rarely es·trum

[es-truhs]

noun

Zoology.

1. the period of heat or rut; the period of maximum sexual receptivity of a female mammal.

2. estrous cycle.

estrus

/ ˈɛstrəs, ˈiːstrəs /

noun

1. the usual US spelling of oestrus

estrus

1. A regularly recurring period in female mammals other than humans during which the animal is sexually receptive. Estrus occurs around the time of ovulation.

2. Also called heat

Other Word Forms

• estrous adjective

Word History and Origins

Origin of estrus¹

First recorded in 1885–90; from Latin oestrus oestrus

Example Sentences

Cats reproduce when females begin estrus, more commonly known as “going into heat,” during which hormones and behavior changes signal she’s ready to mate.

From Salon

But now they must wait until the female rhino is in estrus—the period when the animal is ready to mate—to implant the egg.

From National Geographic

In the other, the whales weren’t pregnant during the first massive progesterone surge, but were instead experiencing a prolonged state of estrus or ovulating.

From New York Times

Otter moms will often go immediately into estrus if they lose a pup.

From Los Angeles Times

Instead, a bull spends his annual two- or three-month stint of erotic drive searching for willing females in estrus, or fighting with other males in musth, all the while eating relatively little.

From New York Times