1. (n.) A carpentry obstruction, stockade, or other obstacle made in a passage in order to stop an enemy.

2. (n.) A fortress or fortified town, on the frontier of a country, commanding an avenue of approach.

3. (n.) A fence or railing to mark the limits of a place, or to keep back a crowd.

4. (n.) An any obstruction; anything which hinders approach or attack.

5. (n.) Any limit or boundary; a line of separation.