any structure that makes progress difficult

a railing at the side of a staircase or balcony to prevent people from falling

a barrier (usually thrown up hastily) to impede the advance of an enemy

a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away

a fencelike structure around a deck (usually plural)

a strong protective barrier that is erected around a racetrack or in the middle of a dual-lane highway in order to reduce the likelihood of severe accidents