Recoil

According to wikipedia:

“ Recoil (often called knockback, kickback or simply kick) is the backward momentum of a gun when it is discharged. ”

The final recoil value when firing a weapon is calculated by combining those of the weapon and ammo used and any installed modifications. The higher this value is, the higher the deviation from the previous shot will be, so low recoil values are desired. This value will keep being calculated and added in every subsequent shot, and along with dispersion it will exponentially increase the chances of missing the target.

You can check the current recoil status in the bottom right side of the screen, where it will be displayed as Recoil, the severity color-coded from light grey to red.

To make sure your next shot won't be under the effects of recoil, wait one turn (5 or .) or move your character one tile until the recoil warning disappears.