Learner's definition of BARRIER
1 : something (such as a fence or natural obstacle) that prevents or blocks movement from one place to another
Concrete barriers surround the racetrack to protect spectators.
The tree's roots serve/act as a barrier against soil erosion.
The mountain range forms a natural barrier between the two countries.
2 a : a law, rule, problem, etc., that makes something difficult or impossible
b : something that makes it difficult for people to understand each other — often + between
Both leaders are in favor of removing trade barriers.
Cultural/social barriers have made it hard for women to enter many professions.
He argues that regulations should not be viewed as barriers to progress.
The lecture was about finding ways to break through barriers between the social classes.
Age can be a big barrier between parents and children.
A language barrier existed between the two countries. [=people in the two countries did not understand each other because they spoke different languages]
3 : a level, amount, or number that is difficult to get past