on·a·ger (?n??-j?r)n.1. A wild ass (Equus hemionus) of Asia, having an erect mane, a light brown coat, and a dark stripe along the back.2. An ancient and medieval catapult, often employing a wooden arm with a short sling.[Middle English, from Late Latin, from Latin, wild ass, from Greek onagros : onos, ass; see asinine + agrios, wild; see agro- in Indo-European roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.onager (??n?d??) n, pl -gri (-??ra?) or -gers1. (Animals) a Persian variety of the wild ass, Equus hemionus. Compare kiang2. (Firearms, Gunnery, Ordnance & Artillery) an ancient war engine for hurling stones[C14: from Late Latin: military engine for stone throwing, from Latin: wild ass, from Greek onagros, from onos ass + agros field]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014on?a?ger (??n ? d??r) n., pl. -gers, -gri (-?gra?) 1. a wild ass, Equus hemionus, of SW Asia. 2. a military catapult used in ancient and medieval times for throwing stones. [1300?50; Middle English