/ ˈbæriə(r); NAmE / noun
1.
an object like a fence that prevents people from moving forward from one place to another :
The crowd had to stand behind barriers.
Show your ticket at the barrier.
—see also crash barrier
2.
barrier (to sth) a problem, rule or situation that prevents sb from doing sth, or that makes sth impossible :
the removal of trade barriers
Lack of confidence is a psychological barrier to success.
3.
barrier (between A and B) | barrier (against sth) something that exists between one thing or person and another and keeps them separate :
The Yangtze river is a natural barrier to the north-east.
There was no real barrier between reality and fantasy in his mind.
Ozone is the earth's barrier against ultra-violet radiation.
the language barrier (= when people cannot communicate because they do not speak the same language)
4.
a particular amount, level or number which it is difficult to get past :
the first player whose earnings passed the $10 million barrier
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WORD ORIGIN
late Middle English (denoting a palisade or fortification defending an entrance): from Old French barriere , of unknown origin.