verb.
To surround or provide with a trench, especially for defense; to dig in.
verb.
To establish a substantial position in business, politics, etc.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
verb.
occupy a trench or secured area
verb.
impinge or infringe upon
verb.
fix firmly or securely
Word Usage
"Even worse, it often does not manifest until the virus has had time to "entrench" itself in the body, making anti-viral drugs somewhat less effective."