(~s)
Frequency: The word is one of the 3000 most common words in English.
1.
A ~ is something such as a rule, law, or policy that makes it difficult or impossible for something to happen or be achieved.
Duties and taxes are the most obvious ~ to free trade.
= obstacle
N-COUNT: oft N to/against/between n
2.
A ~ is a problem that prevents two people or groups from agreeing, communicating, or working with each other.
There is no reason why love shouldn’t cross the age ~...
When you get involved in sports and athletes, a lot of the racial ~s are broken down.
N-COUNT: oft supp N, N between pl-n
3.
A ~ is something such as a fence or wall that is put in place to prevent people from moving easily from one area to another.
The demonstrators broke through heavy police ~s...
As each woman reached the ~ one of the men glanced at her papers.
N-COUNT
4.
A ~ is an object or layer that physically prevents something from moving from one place to another.
...a severe storm, which destroyed a natural ~ between the house and the lake...
The packaging must provide an effective ~ to prevent contamination of the product.
N-COUNT: usu with supp
5.
You can refer to a particular number or amount as a ~ when you think it is significant, because it is difficult or unusual to go above it.
They are fearful that unemployment will soon break the ~ of three million...
N-SING: the N, with supp
6.
see also crash ~ , sound ~