When someone is so stupid/high they think they can spell, but that's just the effect of being illiterate. These people don't even know how completely dumb they are. It's sad.
Person A:"That headache pill is making me illusionating."
Person B: "I'm sure you mean to say 'hallucinate' rather?"
Person A: "oh, my bad, I'm a fucking idiot that can't spell anything and I don't know words."