The Collaborative International Dictionary of English v.0.48:

Circumvallate \Cir`cum*val"late\, v. t. [L. circumvallatus, p.
   p. of circumvallare to surround with a wall; circum + vallare
   to wall, fr. vallum rampart.]
   To surround with a rampart or wall. --Johnson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Circumvallate \Cir`cum*val"late\, a.
   1. Surrounded with a wall; inclosed with a rampart.
      [1913 Webster]

   2. (Anat.) Surrounded by a ridge or elevation; as, the
      circumvallate papill[ae], near the base of the tongue.
      [1913 Webster]

WordNet (r) 3.0 (2006):

circumvallate
    v 1: surround with or as if with a rampart or other
         fortification