catapult vs onager

catapult and onager both are nouns.

Word	Noun	Adjective	Verb	Adverb
catapult	Yes	No	Yes	No
onager	Yes	No	No	No

As nouns, onager is a hyponym of catapult; that is, onager is a word with a more specific, narrower meaning than catapult:

catapult: an engine that provided medieval artillery used during sieges; a heavy war engine for hurling large stones and other missiles
onager: small catapult used by the Romans

Other hyponyms of catapult include trebuchet, trebucket, bricole, mangonel, traction trebuchet.

catapult (noun)	onager (noun)
an engine that provided medieval artillery used during sieges; a heavy war engine for hurling large stones and other missiles	Asiatic wild ass
a plaything consisting of a Y-shaped stick with elastic between the arms; used to propel small stones	small catapult used by the Romans
a device that launches aircraft from a warship

catapult (verb)	onager (verb)
shoot forth or launch, as if from a catapult
hurl as if with a sling