a. [ See oestrus. ] (Physiol.) Of or pertaining to sexual desire; -- mostly applied to brute animals; as, the oestrual period; oestrual influence. [ 1913 Webster ]

n. (Physiol.) The state of being under oestrual influence, or of having sexual desire. [ 1913 Webster ]

‖n. [ L., a gadfly; also, frenzy, fr. Gr. &unr_; gadfly; hence, sting, fury, insane desire, frenzy. ] 1. (Zool.) A genus of gadflies. The species which deposits its larvae in the nasal cavities of sheep is oestrus ovis. [ 1913 Webster ]

2. A vehement desire. [ 1913 Webster ]

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 ]