oes·trus n.
 1. Zool. A genus of gadflies. The species which deposits its larvae in the nasal cavities of sheep is oestrus 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.
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 Gad·fly n.; pl. Gadflies   Zool. Any dipterous insect of the genus Oestrus, and allied genera of botflies.
 Note: ☞ The sheep gadfly (Oestrus ovis) deposits its young in the nostrils of sheep, and the larvæ develop in the frontal sinuses. The common species which infests cattle (Hypoderma bovis) deposits its eggs upon or in the skin where the larvæ or bots live and produce sores called wormels. The gadflies of the horse produce the intestinal parasites called bots. See Botfly, and Bots. The true horseflies are often erroneously called gadflies, and the true gadflies are sometimes incorrectly called breeze flies.
 Gadfly petrel Zool., one of several small petrels of the genus Oestrelata.
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 Oestrus ovis
      n : larvae are parasitic on sheep [syn: sheep botfly, sheep
          gadfly]