Cant
Tilting the rifle left or right of vertical at the moment of the shot. At distance, even a few degrees of cant moves point of impact off the target.
A rifle canted 5 degrees to the right at 1,000 yards can shift impact several feet horizontally. Gravity acts straight down regardless of the rifle’s orientation. A scope-mounted bubble level (anti-cant indicator) is standard on precision rifles for this reason.
Inside 300 yards cant is negligible. Past 600 it becomes a measurable error. Past 1,000 it’s a miss.