If a bad or undesirable situation is your fault, you caused it or are responsible for it.

A fault is a mistake in what someone is doing or in what they have done.

A fault in someone or something is a weakness in them or something that is not perfect.

If you cannot fault someone, you cannot find any reason for criticizing them or the things that they are doing.

A fault is a large crack in the surface of the earth.

A fault in tennis is a service that is wrong according to the rules.

If someone or something is at fault, they are to blame or are responsible for a particular situation that has gone wrong.

If you find fault with something or someone, you look for mistakes and complain about them.

If you say that someone has a particular good quality to a fault, you are emphasizing that they have more of this quality than is usual or necessary.