An unreasonably late hour to start doing anything.
"Hey, wanna watch the Extended Edition of Lord of the Rings?"
"Fuck, no, it's like butt o'clock. Why didn't you ask earlier?"
by WestBranchCaptain December 20, 2011
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Often the wee morning hours at which the possibility of doing something reasonable is slim.

An hour of the day at which said activity is least probable to occur.

The hour at which butt fucking is most likely to occur.
A: Hey, what time do you have to be at work tomorrow?

B: Eh, at butt fuck o'clock unfortunately.

A: So... what precisely goes on at that hour again?
by Loftus Pennyweather March 13, 2013
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