Dimensional Rift is a slang term used to describe a person who's so out of touch with reality, they've basically created their own alternate universe where their nonsense is absolute truth. It's often used to mock someone who's delusional, overly dramatic, or just plain ignorant.

Example:
"Man, did you see how he talked about aliens during the meeting? He’s definitely in a dimensional rift—no one’s even sure if he’s still on Earth."

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