Interrupt
Interrupt is an obselete card type. It has not been supported by the game since Sixth Edition.
Under the original rules, an interrupt was a spell that would resolve before the rest of the Batch. Some examples of interrupts include Counterspell, Red Elemental Blast and Dark Ritual. All Interrupt cards have received errata to make them instants, and all references to Interrupts have been given errata to reference instants.