Cormacing occurs when someone's internet is so trash, that it cosmic ddos anything it comes into contact with. It is so horrible that it affects everything and everyone else using the same service, and can cause others' connection to suffer or even crash as a result.
I was having fun with some friends last night on Xbox, until some guy joined and began cormacing the whole party.
Refers to a killstreak in Call of Duty: Modern Warfare 2, where a UAV (unarmed aerial vehicle) would indicate the location of enemies on the minimap. Similarly, cracking the UAV means looking for woman to have sex with.