The Full Form of ASAT is Anti-satellite.

Anti-satellite weapons (ASAT) are space weapons designed to incapacitate or destroy satellites for strategic military purposes. Several nations possess operational ASAT systems. Although no ASAT system has yet been utilised in warfare, a few nations have shot down their own satellites to demonstrate their ASAT capabilities in a show of force. Only the United States, Russia, China, and India have demonstrated this capability successfully. The roles include: a defensive measure against an adversary’s space-based nuclear and weapons, a force multiplier for a nuclear first strike, a countermeasure against an adversary’s anti-ballistic missile defense (ABM), an asymmetric counter to a technologically superior adversary, and a counter-value weapon.