es·​trus | \ˈe-strəs \

Definition of estrus 

: 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

Females go into estrus for only a couple days annually, and Mei Xiang and her mate, Tian Tian, have previously encountered difficulties with natural conception. Katherine J. Wu, Smithsonian, "Giant Panda Mei Xiang Will Not Give Birth," 5 July 2018 By killing cubs that aren’t his, the male forces the female back into estrus, allowing him to mate and sire cubs of his own. Doug Main, National Geographic, "Why These Leopard Sisters Are Mating With the Same Male," 27 June 2018 Wild cheetahs may go into estrus and become pregnant at any time throughout the year. Jackson Landers, Smithsonian, "Two Litters of Adorable Cheetah Cubs Born in One Week," 7 Apr. 2017 Mei Xiang, who is 18 years old and has birthed three cubs at the zoo, has been showing signs over the past few weeks of being in estrus. Dana Hedgpeth, Washington Post, "National Zoo’s giant panda is in heat and may be ready to breed soon," 23 May 2017 Making their jobs more difficult, mares can come into estrus a mere six days after giving birth. National Geographic, "Can Birth Control Save Our Wild Horses?," 31 Oct. 2016 But one of the females was in estrus, her rump exceptionally pink and swollen, and four males in the group were too excited to sleep. Natalie Angier, New York Times, "Sign Up for the Science Times Newsletter," 10 Sep. 2016

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'estrus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of estrus

circa 1890, in the meaning defined above

History and Etymology for estrus

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

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Dictionary Entries near estrus


estrous cycle






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The first known use of estrus was circa 1890

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es·​trus | \ˈes-trəs \
variants: or estrum \ -​trəm \ or chiefly British oestrus \ ˈē-​strəs \ or oestrum \ ˈē-​strəm \

Medical Definition of estrus 

1a : 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

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