Sacrifice, often abbreviated as Sac, is a keyword action. It means to move a permanent you control to its owner’s graveyard.
Saccing or Sacrificing is purposely or forcefully removing a permanent from play. This can be due to an effect on the card itself, the effect of another permanent already in play, coming into or leaving play or a spell such as a instant or sorcery. A sacrificed permanent cannot be regenerated. Even though the card Sacrifice was in Alpha, the keyword action of sacrifice didn't show up until Revised Edition. 
From the Comprehensive Rules
(Battle for Zendikar
(September 26, 2015
- 701.14a To sacrifice a permanent, its controller moves it from the battlefield directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent he or she doesn’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action.
- Arms Dealer -
Creature - Goblin 1/1
, Sacrifice a Goblin: Arms Dealer deals 4 damage to target creature.
- Cruel Edict -
Target opponent sacrifices a creature.
Creatures that prevent/prohibit sacrificing[edit | edit source]