oestrus
noun /ˈiːstrəs/
/ˈestrəs/
(British English) (North American English estrus)
[uncountable] (specialist)- a period of time in which a female animal is fertile and ready to have sex
compare be on heat(雌性动物的)动情期 词源late 17th cent.: from Greek oistros ‘gadfly or frenzy’.