Cover

Cover is a mechanic, that reduces the hit-chance of a target shooting you from a specific direction, if you currently benefit from it.

Cover applies when you are behind an obstacle, you can still see over, but is not negligible enough to be considered too small for cover. Barrels and windows are a prime example of cover. When standing behind a window, or a barrel, enemies that shoot you only from the other side of it, will receive a 40% hit-chance penalty. (50% with Barricade Tactician. Cover only benefits you from bullets coming from the direction of the cover, and will not help you if an enemy flanks you for example.

When deploying a weapon with $D$, you also get a minor 10% bonus to cover. (20% with Barricade Tactician.