Air in poker is defined as giving a player the leeway to know if or when you intend to pull a card or a lot of them so that the player will be induced to make a call. Giving air in any lowball game of poker is like nudging your opponent to believe something you know to be a hollow threat and getting the player to make an alarmed call. To further explain this term, letting off "air" is akin to blowing hot air and calling for smoke where there is no fire.
When air happens or is called, it is seen as having the upper hand in the game whereas the extent to which the advantage is used depends on how experienced the poker player is in the game. A good poker player can 'create' an air and use the opportunity to change the way the game is going in his favor. However, a learner or someone who is new to the game may find out that it does not really suit their style of play.