howitzer vs trench mortar

howitzer and trench mortar both are nouns.

Word	Noun	Adjective	Verb	Adverb
howitzer	Yes	No	No	No
trench mortar	Yes	No	No	No

As nouns, howitzer and trench mortar are synonyms defined as:

howitzer and trench mortar: a muzzle-loading high-angle gun with a short barrel that fires shells at high elevations for a short range

Other synonyms of howitzer include mortar.

howitzer (noun)	trench mortar (noun)
a muzzle-loading high-angle gun with a short barrel that fires shells at high elevations for a short range	a muzzle-loading high-angle gun with a short barrel that fires shells at high elevations for a short range