definition barrier
Barriers are walls, either physical or metaphorical. They can block movement â the Great Wall of China was a barrier to block invading forces from entering. A window shade is a light barrier. Failing English is a barrier to getting into Harvard. When people are being excluded from joining a clique, you could say that the clique has erected a social barrier. When fighter jets fly faster than the speed of sound, they break through what feels like a wall in the sky called the sound barrier.