trench mortar vs howitzer

trench mortar and howitzer both are nouns.

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

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

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

Other synonyms of trench mortar include mortar.

trench mortar (noun)	howitzer (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