On·a·ger n.; pl. L. Onagri E. Onagers
  1. Rom. Antiq. A military engine acting like a sling, which threw stones from a bag or wooden bucket, and was operated by machinery.
  2. Zool. A wild ass of central Asia, especially the koulan (Equus hemionus syn. Equus hemippus syn. Equus onager, formely Asinus onager).
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  onager
       n 1: medieval artillery used during sieges; a heavy war engine
            for hurling large stones and other missiles [syn: catapult,
             arbalest, arbalist, ballista, bricole, mangonel,
             trebuchet, trebucket]
       2: Asiatic wild ass [syn: Equus hemionus]
       [also: onagri (pl)]