Onager \On"a*ger\, n.; pl. L. {Onagri}, E. {Onagers}. [L. onager, onagrus, Gr. ?.] 1. (Rom. Antiq.) A military engine acting like a sling, which threw stones from a bag or wooden bucket, and was operated by machinery. --Fairholt. [1913 Webster] 2. (Zool.) A wild ass of central Asia, especially the {koulan} ({Equus hemionus} syn. {Equus hemippus} syn. {Equus onager}, formely {Asinus onager}). [1913 Webster +PJC]