Real Dictionary

barrier
adherence to moral principles; honesty [...]
any disturbance or abnormality in the function of an organ or part [...]
anything serving to obstruct passage or to maintain separation, such as a fence or gate [...]
the natural action or intended purpose of a person or thing in a specific role [...]
countable noun: A barrier is a problem that prevents two people or groups from agreeing, communicating, or working with each other.
countable noun: A barrier is an object or layer that physically prevents something from moving from one place to another.
countable noun: A barrier is something such as a fence or wall that is put in place to prevent people from moving easily from one area to another.
countable noun: A barrier is something such as a rule, law, or policy that makes it difficult or impossible for something to happen or be achieved.
singular noun: You can refer to a particular number or amount as a barrier when you think it is significant, because it is difficult or unusual to go above it.