entrench

Short definition from Wiktionary

Verb

1. 1
   To cut in; to furrow; to make trenches in or upon.
2. 2
   To cut in; to furrow; to make trenches in or upon: To dig or excavate a trench; to trench.
3. 3
   To cut in; to furrow; to make trenches in or upon: To surround or provide with a trench, especially for defense; to dig in.
4. 4
   To become completely absorbed in and fully accept one's beliefs, even in the face of evidence against it and refusing to be reasoned with.
5. 5
   To establish a substantial position in business, politics, etc.
6. 6
   To invade; to encroach; to infringe or trespass; to enter on, and take possession of, that which belongs to another; usually followed by on or upon.