1. To pretend to play a instrument, like air guitar

2. To fake something

In Slang term, it means "Blank" which is ignoring someone.

Being ignored by someone when making a statement or asking a question. Also known as blanked and turfed.

basically means blanking someone which is when you heard/read what they said but you ignore then and don't reply

Air is mostly nitrogen and oxygen and water vapor. We breathe it.

When Some one gets blanked or ignored by somebody.

what you give to someone who has annoyed you. giving air is the same as 'blanking' someone