To make a trench or furrow in; furrow; cut.To surround as with a trench or ditch.To fortify with a trench or ditch and parapet; strengthen or protect by walls of defense: as, to intrench a camp or an army.Hence To fortify or defend by any protecting agency; surround with or guard by anything that affords additional security against attack.To invade; encroach: with on or upon.Synonyms Encroach upon, Infringe upon, etc. See trespass, v.i.To incise; cut down or deepen the valley of (a stream).