The period of sexual quiescence between the estrus cycles of mammals; may be: 1) a prolonged period in monestrous animals (dogs) or seasonally polyestrous animals (sheep), or 2) a prolonged period of failure of estrus in mature nonpregnant, polyestrous animals. [G. a- priv. + oistros, a gadfly, mad desire (estrus)]
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an·es·trus or chiefly Brit an·oes·trus -trəs n the period of sexual quiescence between two periods of sexual activity in cyclically breeding mammals compare ESTRUS
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an·es·trus (an-esґtrəs) 1. abnormal lack of ovarian activity in a female mammal; the term is sometimes extended to include any prolonged lack of sexual responsiveness. 2. a period of the estrous cycle during which there is no ovarian activity; in cats, horses, sheep, goats, and certain other species this occurs annually for periods of weeks to months. Called also diestrus.Medical dictionary. 2011.