| Main Entry: | active barrier1 |
| Part of Speech: | n |
| Definition: | an object that prevents passage of certain entities but allows passage of predefined entities, esp. a chemical or physical barricade for contaminants or debris |
| Main Entry: | active barrier2 |
| Part of Speech: | n |
| Definition: | a movable object that prevents passage of certain entities but allows passage of predefined entities, esp. a security barricade |
| Example: | A sliding gate is an active barrier; a retaining wall is a passive barrier. |