Select the most appropriate meaning of the given idiom.

Vanish into the air

Completely disappear

The most appropriate meaning of the idiom "vanish into the air" is completely disappear.

The idiom is used to describe something that disappears suddenly and completely, as if it had never existed. It is often used to describe something that is very fragile or delicate, such as a dream or a hope.

For example, you might say "My hopes of winning the lottery vanished into thin air." or "The dream of a peaceful world vanished into the air with the outbreak of war."

The other options are not as appropriate. To perpetually postpone means to keep putting something off indefinitely. To totally dilute means to make something so weak that it is no longer effective. To permanently mix means to combine something with something else so that they cannot be separated.