A split is the horizontal distance between two offensive lineman when they are in the formation.
Splits vary by the offense, coach and situation. When the offense lines up with wide splits they create large gaps. Those gaps can be run through by a ball carrier or a defender. When the offense lines up with tighter splits there is less room to run between them. Tighter splits allow offensive lineman to more easily double team defenders and block defenders that aren’t lined up directly across from them.
Most defensive fronts line up on the offensive lineman. For instance a particular defensive tackle who is supposed to line up on a guard’s outside shoulder will do that whether the guard is two feet or four feet away from the center. If the splits become too wide, the defense may adjust its alignment to take advantage of the holes.
Gridiron Glossary is a resource for football terms that are often used by commentators, coaches and players but rarely defined. If there is a term you have questions about or a definition you don’t agree with, let me know at email@example.com.