Line of Fire: Hindering terrain impede
line of fire. If a line of fire between two
characters is hindered, modify the target’s
defense value by +1 for the attack, unless
the only square of hindering terrain
crossed is occupied by the attacker.

Any line of fire or path of movement that crosses hindering terrain (including the square occupied by the target) is labeled a “hindered” line of fire or path of movement.