Alpha strike

An alpha strike refers to an all-out attack, in which a player (more often than not, who believes that he or she will win from that attack) aims to deal a lethal amount of damage to the opponent. Since this leaves the attacker defenseless, it is generally used when the attacking player is positive that their attack will result in a win. Such attacks are often accompanied by spells or abilities (such as Overrun, Garruk Wildspeaker, or Relentless Assault) that will create a nearly hopeless situation for the opponent.

Etymology
The term comes from the computer game MechWarrior, where it describes the firing of all of the player's weapons simultaneously.