abatis

abatis
    n 1: a line of defense consisting of a barrier of felled or live
         trees with branches (sharpened or with barbed wire
         entwined) pointed toward the enemy [syn: {abattis},
         {abatis}]
    

Abatis \Ab"a*tis\, Abattis \Aba"t*tis\, ([a^]b"[.a]*t[i^]s;
   French [.a]`b[.a]`t[=e]") n. [F. abatis, abattis, mass of
   things beaten or cut down, fr. abattre. See {Abate}.] (Fort.)
   A means of defense formed by felled trees, the ends of whose
   branches are sharpened and directed outwards, or against the
   enemy.
   [1913 Webster]
    

ABATIS, n.  Rubbish in front of a fort, to prevent the rubbish outside
from molesting the rubbish inside.
    

56 Moby Thesaurus words for "abatis":
      advanced work, balistraria, bank, banquette,
      barbed-wire entanglement, barbican, barricade, barrier, bartizan,
      bastion, battlement, breastwork, bulwark, casemate,
      cheval-de-frise, circumvallation, contravallation, counterscarp,
      curtain, demibastion, dike, drawbridge, earthwork, enclosure,
      entanglement, escarp, escarpment, fence, fieldwork, fortalice,
      fortification, glacis, loophole, lunette, machicolation, mantelet,
      merlon, mound, outwork, palisade, parados, parapet, portcullis,
      postern gate, rampart, ravelin, redan, redoubt, sally port, scarp,
      sconce, stockade, tenaille, vallation, vallum, work