1. a structure or object that impedes free movement
(hypernym) obstruction, obstructor, obstructer, impediment, impedimenta
(hyponym) bannister, banister, balustrade, balusters, handrail
2. any condition that makes it difficult to make progress or to achieve an objective; "intolerance is a barrier to understanding"
(hypernym) obstacle, obstruction
(hyponym) ideological barrier
3. anything serving to maintain separation by obstructing vision or access