1. barrier, obstruction, obstructor, obstructer, impediment, impedimenta

usage: a structure or object that impedes free movement

2. barrier, roadblock, obstacle, obstruction

usage: any condition that makes it difficult to make progress or to achieve an objective; "intolerance is a barrier to understanding"

3. barrier, mechanism

usage: anything serving to maintain separation by obstructing vision or access

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See also: barrier (Dictionary)