- The definition of a fortress is a secured and strong place.
An example of a fortress is a wall made out of stone that protects a city.
Edinburgh Castle is a fortress.
fortress definition by Webster's New World
Origin: Middle English forteresse ; from Old French ; from Vulgar Latin an unverified form fortaricia ; from Classical Latin fortis, strong: see fort
fortress definition by American Heritage Dictionary
Origin: Middle English forteress, from Old French, from Medieval Latin fortalitia, from Latin fortis, strong; see bhergh-2 in Indo-European roots.