*barrier*

n. [ OE. barrere, barere, F. barrière, fr. barre bar. See Bar, n. ] 1. (Fort.) A carpentry obstruction, stockade, or other obstacle made in a passage in order to stop an enemy. [ 1913 Webster ]

2. A fortress or fortified town, on the frontier of a country, commanding an avenue of approach. [ 1913 Webster ]

3. pl. A fence or railing to mark the limits of a place, or to keep back a crowd. [ 1913 Webster ]

No sooner were the barriers opened, than he paced into the lists. Sir W. Scott. [ 1913 Webster ]

4. Any obstruction; anything which hinders approach or attack. “Constitutional barriers.” Hopkinson. [ 1913 Webster ]

5. Any limit or boundary; a line of separation. [ 1913 Webster ]

'Twixt that [ instinct ] and reason, what a nice barrier! Pope. [ 1913 Webster ]

Barrier gate, a heavy gate to close the opening through a barrier. --
Barrier reef, a form of coral reef which runs in the general direction of the shore, and incloses a lagoon channel more or less extensive. --
To fight at barriers, to fight with a barrier between, as a martial exercise. [ Obs. ] [ 1913 Webster ]