noun any limit or boundary; a line of separation.
2. barrier ·noun an any obstruction; anything which hinders approach or attack.
3. barrier ·noun a fence or railing to mark the limits of a place, or to keep back a crowd.
4. barrier ·noun a fortress or fortified town, on the frontier of a country, commanding an avenue of approach.
5. barrier ·noun a carpentry obstruction, stockade, or other obstacle made in a passage in order to stop an enemy.