PK

Stands For
Penalty Kill

Which means
In hockey, when the opposing team is on the power play, your team is on the penalty kill. In most cases, an extra defenceman is placed on the ice to prevent the other team from scoring.

Example
Hockey Player: We only won the game because we worked so hard on the PK.

Related Acronyms

 * PP

Stands For
Player Kill(ing)

Which means
In the MMORPG Runescape, there are certain areas where players can attack and "kill" each other. The act of doing that is called PKing.

Example
Joe: I lost all my items after being PKed in the Bounty Hunter minigame last night.

Related Acronyms

 * RS
 * MMORPG