barrier
1.
2.
3.
4. A boundary or limit.
5. Something that separates or holds apart.
6. A movable gate that keeps racehorses in line before the start of a race.
7. The palisades or fences enclosing the lists of a medieval tournament. Often used in the plural.
8. Geology. An ice barrier.
[Middle English barrer, from Old French barriere, from Vulgar Latin *barrāria, from *barra, bar.]