1. An action that causes immediate aggravation and hostility from those around you
Origin- Slang term for the spell "Prayer of Healing" used by priests in World of Warcraft. In early versions of the game, it was infamous for generating large amounts of aggro, making it almost unusable in group or raid settings. Later updates have lessened the amount or importance of aggro, but the name is still used in some circles.
see also- aggro bomb
"Things were going great until I cast prayer of aggro and I got rofled by adds!"