barrier

noun

1. A structure that bars passage.

   “The bus went through a railway barrier and was hit by a train.”

   “The bomber had passed through one checkpoint before blowing himself up at a second barrier.”

2. An obstacle or impediment.

   “Even a small fee can be a barrier for some students.”

   “America’s poverty line is $63 a day for a family of four. In the richer parts of the emerging world $4 a day is the poverty barrier. But poverty’s scourge is fiercest below $1.25 ([…]): people below that level live lives that are poor, nasty, brutish and short.”

3. A boundary or limit.

   “Few marathon runners break the three-hour time barrier.”

   “The downside of normalization is that it erects a defensive barrier between the real world and the perceived i.e. normalized world.”

4. A node (in government and binding theory) said to intervene between other nodes A and B if it is a potential governor for B, c-commands B, and does not c-command A.
5. A separation between two areas of the body where specialized cells allow the entry of certain substances but prevent the entry of others.
6. (historical)The lists in a tournament.
7. (historical, in-plural)A martial exercise of the 15th and 16th centuries.

verb

1. (transitive)To block or obstruct with a barrier.

name

1. A surname from French.