Real Dictionary

trench
A trench is a long narrow channel in the ground used by soldiers in order to protect themselves from the enemy. People often refer to the battle grounds of the First World War in Northern France and Belgium as the trenches.
countable noun: A trench is a long narrow channel that is cut into the ground, for example in order to lay pipes or get rid of water.

trench in American English
a deep furrow in the ground, ocean floor, etc.
to cut, cut into, cut off, etc.; slice, gash, etc.
to dig a ditch or ditches, as for fortification
intransitive verb: to dig a trench
noun: a long, narrow excavation in the ground, the earth from which is thrown up in front to serve as a shelter from enemy fire or attack
transitive verb: to surround or fortify with trenches; entrench

trench in British English
noun: a deep ditch or furrow
verb: to make a trench in (a place)