1. verb/0 Abbreviation of 'player killing': the concept of allowing one persona to attack and destroy another persona. Some MUAs don't allow PKing (proudly so!), others do (also proudly so!). Both extremes can lead to game management difficulties. See HCDS.
2. noun A persona which indulges in PK in the above sense. This use probably arose to complement PC (sense 4) and is now the dominant form. "Any PKs on?". This dictionary, however, prefers the more technically accurate term killer to PK. See APK.

PK is usually, but not always, capitalised.