The term "trench mortar" is correct and usable in written English.
You can use it to refer to a type of weapon consisting of a short, medium, or long tube from which bombs or shells are fired at an angle, usually at a high trajectory. For example, "The infantry used their trench mortars to drive the enemy from their position."
I don't expect you've ever heard a trench mortar, but it's a strange sound.
Some rebel units have consisted of no more than a sniper, a machine gunner and a fighter with a trench mortar.
The 9.45-inch heavy mortar equipped a heavy trench mortar battery, while medium trench mortar batteries were equipped with the 2-inch mortar mortand and later the 6-inch mortar.
In addition Pasha I also included two trench mortar companies, the 300th Flight Detachment, Wireless detachment, three railway companies and two field hospitals.
The remnants of the 702nd and the 703rd Battalions were formed into a battalion to which a rifle company, a machine gun company and a trench mortar detachment were attached.
The 701st Battalion with its machine gun company of six guns, a troop of cavalry, an infantry-artillery platoon with two mountain guns or howitzers and a trench mortar section with four mortars and a cavalry squadron, remained intact.
Our trench mortars are wonderful things.
Field mines and booby traps were used extensively, and trench mortars were developed to lob shells into opposing trenches.
They took a hundred and eighteen, and, for the most part, neglected to bring howitzers, trench mortars, or grenades.
You see the mountains of shells, from the "plum puddings" for the trench mortars to the "grandmothers" for the 15in.
The roll-call of the thinned ranks is recorded, regiments have a good wash in a wayside pool, guns and trench mortars and other booty are wheeled off to the rear.
