In basketball, this is an unblocked shot that doesn't touch the rim or the backboard.
An air ball is typically regarded as the most embarrassing thing a player can do on the court. When a player shoots an air ball while playing on the road, the home crowd typically chants "air ball" in a sing-song manner afterwards to remind the player how incompetent he is.
Some air balls are so horrible that they don't even count as a field goal attempt. It's typically up to the scorekeeper's discretion whether an air ball counts as an attempt or not. The shot clock does not reset after an air ball. Also, if the shooting player touches his own air ball without the opposing team touching the ball first, the player will be whistled down for travelling.