Seriously, genuinely, no joke — 'deadass, that happened' — from New York into the internet by 2016, and one of the few slang words of the 2010s that is still used sincerely without a wink. The record files it as a survivor.
The record spells it one way; the original post spelled it another. I would keep the original, typo and all. The typo is the provenance.
Most emphatic slang dies of irony within three years. Deadass is ten years old and still means what it says. The record does not know why and has decided to respect it.
What does it mean? Write it the way you would say it out loud.
