estrus

noun

es·​trus ˈe-strəs 

: a regularly recurrent state of sexual receptivity during which the female of most mammals will accept the male and is capable of conceiving : heat

Some mares will exhibit estrus for 15 to 20 days.

—Frederick Harper

also : a single occurrence of this state

Examples of estrus in a Sentence

Recent Examples on the Web

So as part of managing this, female giraffes may be given a daily dose of liquid birth control to keep them from cycling into estrus during certain time periods. —Jim Higgins, jsonline.com, 8 July 2025

Fortunately, Willow was not in estrus, preventing an unwanted pregnancy, but the incident still resulted in a costly emergency visit. —Lydia Patrick, Newsweek, 18 Mar. 2025

During the rut, bucks might even push estrus does into such areas to get them away from rival bucks. —Josh Honeycutt, Outdoor Life, 14 Nov. 2024

Electricity is used to stimulate cell division, and, when this embryo is still just a bundle of cells on the scale of micrometres, a second dog, also in estrus, is operated on to become a surrogate mother. —Alexandra Horowitz, The New Yorker, 24 June 2024

Word History

Etymology

New Latin, from Latin oestrus gadfly, frenzy, from Greek oistros — more at ire

First Known Use

circa 1890, in the meaning defined above

Rhymes for estrus

• estrous

Kids Definition

estrus

noun

es·​trus ˈes-trəs 

1

: a periodic state during which the female of most mammals is willing to mate with the male and is capable of becoming pregnant

2

: estrous cycle

estrous

-trəs

adjective

Medical Definition

estrus

noun

es·​trus ˈes-trəs 

variants or estrum

-trəm 

or chiefly British oestrus

ˈē-strəs 

or oestrum

ˈē-strəm 

1

a

: a regularly recurrent state of sexual excitability during which the female of most mammals will accept the male and is capable of conceiving : heat

b

: a single occurrence of this state

2

: estrous cycle