Oestrus n. : A genus of gadflies. The species which deposits its larvae in the nasal cavities of sheep is oestrus ovis.

Oestrus n. : A vehement desire; esp. (Physiol.), the periodical sexual impulse of animals; heat; rut.

Example:
what hormones are released during the Oestrus cycle?

Taxonomy
estrus, cycle, estrous cycle, estrous cycles, diestrus, Anestrus, oestrus, mammalian species, herd animals, menstrual cycle, proestrus, pregnancy, phases, Horses, mammals, gadfly, Humans, female cat in heat.

Defination from the web:
oestrus and originally from Greek οἶστρος) comprises the recurring physiologic changes ... Euripides used "oestrus" to indicate "frenzy", and to describe madness. ...