Merriam-Webster Collegiate Dictionary - trench

 I. noun  Etymology: Middle English ~e track cut through a wood, from Anglo-French, act of cutting, ditch, from ~er, ~ier to cut, probably from Vulgar Latin *trinicare to cut in three, from Latin trini three each — more at trine  Date: 15th century  1.  a. a long cut in the ground ; ditch; especially one used for military defense often with the excavated dirt thrown up in front  b. plural a place, position, or level at which an activity is carried on in a manner likened to ~ warfare — often used in the phrase in the ~es activists working in the ~es  2. a long, narrow, and usually steep-sided depression in the ocean floor — compare trough  3. ~ coat  II. verb  Date: 15th century  transitive verb  1. to make a cut in ; carve  2.  a. to protect with or as if with a ~  b. to cut a ~ in ; ditch  intransitive verb  1.  a. en~, encroach ~ing on other domains which were more vital — Sir Winston Churchill  b. to come close ; verge  2. to dig a ~