1. [n]  a hole in the ground made by an animal for shelter
2. [v]  move through by or as by digging; "burrow through the forest"

BURROW is a 6 letter word that starts with B.

1. \Bur"row\, n. [See 1st {Borough}.]
   1. An incorporated town. See 1st {Borough}.
   
   2. A shelter; esp. a hole in the ground made by certain
      animals, as rabbits, for shelter and habitation.
   
   3. (Mining) A heap or heaps of rubbish or refuse.
   
   4. A mound. See 3d {Barrow}, and {Camp}, n., 5.
   
   

2. \Bur"row\, v. i. [imp. & p. p. {Burrowed}; p. pr. & vb.
   n. {Burrowing}.]
   1. To excavate a hole to lodge in, as in the earth; to lodge
      in a hole excavated in the earth, as conies or rabbits.
   
   2. To lodge, or take refuge, in any deep or concealed place;
      to hide.
   
            Sir, this vermin of court reporters, when they are
            forced into day upon one point, are sure to burrow
            in another.                           --Burke.
   
   {Burrowing owl} (Zo["o]l.), a small owl of the western part
      of North America ({Speotyto cunicularia}), which lives in
      holes, often in company with the prairie dog.