what does the “TMI” mean？
“So, I keep having these weird dreams,” he adds.
I raise my eyebrows. “Yikes. TMI?”
“Um. Not that kind of dream.”

Question

Answer

Hello ! It might be the acronym for :" Too Much Information" - way more than you need/want to know about someone.
http://www.urbandictionary.com/define.php?term=TMI
Hope it helps =)

Answer

It means "Too Much Information". This might mean information that is too personal or graphic.

In your example, one of the speakers thought his/her friend was about to reveal something far too intimate.

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