The Collaborative International Dictionary of English v.0.48:

Intrench \In*trench"\, v. t. [imp. & p. p. Intrenched; p. pr.
   & vb. n. Intrenching.]
   [1913 Webster]
   1. To cut in; to furrow; to make trenches in or upon.
      [1913 Webster]

            It was this very sword intrenched it. --Shak.
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            His face
            Deep scars of thunder had intrenched. --Milton.
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   2. To surround with a trench or with intrenchments, as in
      fortification; to fortify with a ditch and parapet; as,
      the army intrenched their camp, or intrenched itself. "In
      the suburbs close intrenched." --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Intrench \In*trench"\, v. i.
   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; as, the king was charged with
   intrenching on the rights of the nobles, and the nobles were
   accused of intrenching on the prerogative of the crown.
   [1913 Webster]

         We are not to intrench upon truth in any conversation,
         but least of all with children.          --Locke.
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WordNet (r) 3.0 (2006):

intrench
    v 1: fix firmly or securely [syn: entrench, intrench]