High Hat is a term for the position of an offensive lineman’s helmet at the start of a passing play.
Many defenses use keys for their players to be able to quickly determine if the play is
a pass or a run. A common key is for a defender to watch the helmet of a particular offensive lineman. If the lineman fires off the ball, he is probably run blocking for a running play. If the lineman stands up he is probably pass blocking. These keys can be simplified into watching the helmet. If the helmet is up or high, it is said to be a high hat to indicate pass. Conversely a low hat indicates run.
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.