What is Barriers?

Barriers definition and meaning on Dictionary terms:
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.