What does Gibraltar stand for on royal marines badge?

It represents the Battle of The Rock of Gibraltar on the 21st July 1704 during the war of Britain (as part of a coalition) against France & Spain. On this day, 1900 Marines & 400 Dutch Marines stormed the island and forced the garrison to surrender, securing the Rock of Gibraltar as a tactical standpoint at the entrance to the Mediterranean Sea. It was seen as one of the outstanding achievements of the Corps and is a reflection of the calibre of men who wear the badge.