A “Gillman” is an unofficial / slang term for a very long pass intended to clear the ball quickly from a team’s defensive zone to their offensive zone.
It is most likely named for Sid Gillman, a legendary football coach who coached from 1938 to 1974.
Gillman’s insistence on stretching the football field by throwing deep downfield passes was instrumental in making football into the modern game that it is today.
A deep, downfield pass on a lacrosse field still bears his name.