anything built or serving to bar passage, as a railing, fence, or the like

People may pass through the barrier only when their train is announced.

any natural bar or obstacle

a mountain barrier.

anything that restrains or obstructs progress, access, etc.

a trade barrier.

a limit or boundary of any kind

the barriers of caste.

Physical Geography . an antarctic ice shelf or ice front.

barrier beach.

barriers, History/Historical . the palisade or railing surrounding the ground where tourneys and jousts were carried on.

Archaic . a fortress or stockade.

noun

opening

noun

bar , barricade , blank wall , blockade , bound , boundary , confines , curtain , ditch , enclosure , fence , fortification , gully , hurdle , impediment , limit , moat , obstacle , pale , palisade , railing , rampart , roadblock , stop , trench , wall , check , difficulty , drawback , encumbrance , handicap , hindrance , limitation , preventive , restraint , restriction , stumbling block , partition , block , blockage , clog , hamper , obstruction , snag , traverse , chain , dam , defense , door , fortress , gate , hedge , line , palisades , parapet , rail , screen , stockade