Definition of "barrier"

barrier

/ˈbæɹi.ə(ɹ)/

noun
plural barriers
1. A structure that bars passage.
2. An obstacle or impediment.
  Quotations
  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.
  2013 June 1, “Towards the end of poverty”, in The Economist‎, volume 407, number 8838, page 11
3. A boundary or limit.
4. (grammar) 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. (physiology) 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 the plural) A martial exercise of the 15th and 16th centuries.
verb
third-person singular simple present barriers, present participle barriering, simple past and past participle barriered
1. (transitive) To block or obstruct with a barrier.