Abatis
Abatis (ab"ȧ*tis; French ȧ`bȧ`tē") , noun
[French abatis, abattis, mass of things beaten or cut down, from abattre. See Abate.]
(Fortification) A means of defense formed by felled trees, the ends of whose branches are sharpened and directed outwards, or against the enemy.
Also: Abattis