An anti-air move is a move with anti-air capability. Alternatively, it refers to a move shoehorned into this service.
Nearly all anti-air moves are a jumping rising uppercut of some sort, like the Shōryūken. It is possible for this to be accompanied or replaced by a projectile hitbox of some sort (e.g., Athena’s Psycho Sword and Dhalsim’s Yoga Blast, respectively).
Some anti-air moves have an invincible hitbox at the beginning. These may be called invincible anti-air moves.