oestrusPronunciation: /ˈiːstrəs, ˈɛstrəs/ (US estrus)Definition of oestrus noun [mass noun] a recurring period of sexual receptivity and fertility in many female mammals; heat:a mare in oestrusDerivatives oestrous adjective Origin: late 17th century: from Greek oistros 'gadfly or frenzy'oestrus in other Oxford dictionaries Definition of oestrus in the US English dictionary
