oestrus

1. (countable) A biting fly of the genus Oestrus; a botfly.Examples: "[…] 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."countable

2. (countable) A bite or sting.countable

3. (countable, archaic) A passion or frenzy.archaiccountable

4. (countable and uncountable, biology) A female animal's readiness to mate.Examples: "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: […]"countableuncountable