Top Definition
When it is so late and your mind is gone, and you just don't care what time it is anymore.
"Dude I'm so wasted, what time is it?"
"I don't know, 100 'o' Clock."
by NoWayDude October 17, 2008
too late or too long
We didn't get home from that party until 100 O'Clock.

It already feels like 100 O'Clock.

This conference lasts until 100 O'Clock.
by smartypants2011 May 17, 2011
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