It is an adjective.
Synonym: Shitty situation that happened but that is amazing because it actually happened
Guy, "Yea it's totally horrificating."
Girl, "Yes, it is totally horrible and unexpected and amazing that someone could actually hack it!"
Guy, "No, its horrificating because I know you hacked it because of that night with the cybering..."
Girl, "Ooh, true." *laughs meniacally*
Guy, "You are horrificating"
Girl, "I know."