trench mortar

a portable, muzzle-loaded mortar, usually having a smooth bore, fired at high angles of elevation to reach concealed enemy targets.

Origin of trench mortar

First recorded in 1915–20

Trench-mortar projectiles are so large, and they describe so leisurely an arc before they fall, that men have time to run.

Prairie Gold |Various
It was a trench-mortar which blew a hole in his body just now, over there.

Now It Can Be Told |Philip Gibbs
Throughout, the crossing was effected under fairly lively machine-gun and trench-mortar fire.

The History of the 51st (Highland) Division 1914-1918 |Frederick William Bewsher
Three 2-inch trench-mortar batteries were formed by the Divisional artillery.

The History of the 51st (Highland) Division 1914-1918 |Frederick William Bewsher

The German who fired the trench-mortar had done better than he knew.

A Company of Tanks |W. H. L. Watson

trench mortar

a portable mortar used in trench warfare to shoot projectiles at a high trajectory over a short range