1) Abatis 2) Barbed-wire barricade 3) Defense made of trees 4) Line of defence 5) Line of defense 
• (n.) A means of defense formed by felled trees, the ends of whose branches are sharpened and directed outwards, or against the enemy.
[n] - line of defense consisting of a barrier of felled or live trees with branches (sharpened or with barbed wire entwined) toward the enemy
abatis noun line of defense consisting of a barrier of felled or live trees with branches (sharpened or with barbed wire entwined) toward the enemy