Oklahoma is a practice drill where one defensive player lines up against an offensive blocker with a running back behind him. The defender must engage the offensive player, beat him and then tackle the running back.
The drill can be very violent, and many coaches no longer practice with it because of the perceived likelihood of injury.
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 firstname.lastname@example.org.