intrench
verb
in·trench in-ˈtrench 
less common spelling of entrench
transitive verb
1
a
: to place within or surround with a trench especially for defense
b
: to place (oneself) in a strong defensive position
c
: to establish solidly
entrenched themselves in the business
2
: to cut into : furrow
specifically : to erode downward so as to form a trench
intransitive verb
1
: to dig or occupy a trench for defensive purposes
2
: to enter upon or take over something unfairly, improperly, or unlawfully : encroach —used with on or upon