Estrus

[преимущественно американский вариант английского языка]; смотри значение oestrus

Большой англо-русский словарь

Estrus

noun Etymology: New Latin, from Latin oestrus gadfly, frenzy, from Greek oistros — more at ire a regularly recurrent state of sexual excitability during which the female of most mammals will accept the male and is capable of conceiving; heat; also a single occurrence of this state

Merriam-Webster's Collegiate Dictionary