When a person says something serious, but hides it using sarcasm.
Girl1: "I tots just saw the way you were looking at your ex! You def still have feelings for him!"
Girl2: "Oh yeah. You're right. I'm still madly in love with him."
Girl1: "I knew it!"
Girl2: "You're so f-ing dumb. That was sarcasm."
Girl1: "No, that was realcasm."