A term used in gaming, most likely stemming from MMORPG lingo, where shortening terms becomes essential for text communication. A
debuff can be used in two similar respects. It replaces the drawn-out phrase "negative status ailment", where an attack or spell causes some ill effect on it's target, i.e. poisoning, silence, bleed.
Debuff can also be used referring to an attack or spell that removes positive
status effects. Many traditional
RPGs have adopted this term as well.