From the ESPN.com Miami Hurricanes board
"GT option is a true Wildcat that the Dolphins run. It is a QB keeper, on a delay, most of the time, and a run up the gut. This is different than the old Nebraska option for which defenses needed speed to catch up to the edge of the field. In GT option you need big stuffers to stuff the middle, and not much speed is needed because action is delayed. So basically a defense needs to delay-blitz the middle , and play man, which is what the Ravens did against the Dolphins in the playoffs last year."
http://boards.espn.go.com/boards/mb/mb?sport=ncaa&id=2390&tid=5382808&lid=6