Select the most appropriate meaning of the given idiom.

Up in the air

Something that is unknown entirely

The most appropriate meaning of the idiom "up in the air" is something that is unknown entirely.

This idiom means that something is uncertain or undecided. It is often used to describe a situation that is not yet clear or a decision that has not yet been made. The idiom comes from the idea of something being literally up in the air, which would make it difficult to know what it is or what will happen to it.

Here are some examples of how the idiom "up in the air" can be used in a sentence:

• The future of the company is still up in the air.
• The negotiations are up in the air and it is unclear what will happen next.
• The plan is still up in the air and we need to wait for more information.