/ trentʃ; NAmE / noun
1.
a long deep hole dug in the ground, for example for carrying away water
2.
a long deep hole dug in the ground in which soldiers can be protected from enemy attacks (for example in northern France and Belgium in the First World War) :
life in the trenches
trench warfare
3.
(also ˌocean ˈtrench ) a long deep narrow hole in the ocean floor
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WORD ORIGIN
late Middle English (in the senses track cut through a wood and sever by cutting ): from Old French trenche (noun), trenchier (verb), based on Latin truncare to maim.