oestrus

noun

1. (countable)A biting fly of the genus Oestrus; a botfly.

   “[…] and which is produced by the larvae of oestri and particularly of Oestrus hemorrhoidalis.”

   “If this is inseparable from the oeconomy of nature, it necessarily follows that man must be subject to the depredations of oestri, ichneumons, . . . and perhaps, thousands of others, which the senses, aided by the directions of a correct understanding, may be able to trace in a way that will fall very little short of absolute demonstration.”

2. (countable)A bite or sting.
3. (archaic, countable)A passion or frenzy.
4. (countable, uncountable)A female animal's readiness to mate.

   “In those monoestrous species in which the male is capable all the year round, it is found that the oestri of individual females come at different seasons.”

   “A vasectomized Philippine carabao bull was used as a teaser to determine the occurrence and recurrence of oestri.”

   “An evaluation was carried out so that the mean number of oestri per one animal was calculated for 14 days in the three periods: […]”

   “Intervals between oestri and between ovulations in dairy cows within 100 days post partum”

   “It’s the supremely human act, freely to fuck, not because you are on heat, or in oestrus, like an animal, but to give and receive pleasure.”