applies to nonhuman mammals: a state or period of heightened sexual arousal and activity
<noun.state>
type genus of the Oestridae: sheep botflies
<noun.animal>
OEstrus \[OE]s"trus\, n. [L., a gadfly; also, frenzy, fr. Gr. ? gadfly; hence, sting, fury, insane desire, frenzy.] 1. (Zo["o]l.) A genus of gadflies. The species which deposits its larv[ae] in the nasal cavities of sheep is {[oe]strus ovis}.
2. A vehement desire.
3. Specifically: (Physiol.) The periodical sexual impulse of animals; the period during which female animals are most receptive to males; heat; rut. [1913 Webster +PJC]