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1.
Very late at night of very early in the morning.
"No can do mate, I've got to be up at stupid o'clock to take the wife to the airport"

"We all sat up drinking to stupid o'clock last night"
by King Midas November 30, 2006
 
2.
Stupid O'Clock is any time after midnight and before 8AM, or hours outside of your natural waking life.
For example, if you have been kept up late and you feel as though you should be asleep, this is stupid O'clock.

See also, 'Stupid Early'.
He came to pick me up at stupid O'clock this morning.. I wan't even awake.
by Eric Booth November 14, 2010
 
3.
Coined by a graduate student while pursuing her PhD and teaching a full load of courses:

The time of day roughly characterized as being between 2:00 am - 6:00 am (depending upon your personal nocturnal patterns and time zone). It is the time when 'normal' people are asleep, because they have to be up and about during working hours the next day. You are exhausted and want very much to be asleep, too. However, you are awake at stupid o'clock because:

(1) you are grouchily doing work to meet a deadline (perhaps because you waited until the last minute to finish it or have perfectionist tendencies),

(2) you haven't yet gone to bed because you are too foolish/lazy to stop goofing off (surfing the net, talking to friends, watching TV/movies, playing video games, reading a book, etc.),

(3) you have to wake up much earlier than your usual time for an important event (which may be an unwanted obligation or an event you desire to attend),

(4) you experience tremendous inspiration and simply cannot stop writing, painting, coding, constructing or otherwise working on your personal project, whatever it might be (a rare usage of the term).
1. I had insomnia, so I was up until stupid o'clock learning new words on Urban Dictionary.
2. I stayed awake until stupid o'clock finishing the paper that was due today.
3. I can't believe I have to get up at stupid o'clock to meet with my idiot boss.
4. We have to leave the house at stupid o'clock to catch our plane.
5. The party lasted until stupid o'clock, but we all had a lot of fun!
6. Why, yes, it WAS stupid o'clock when I composed this entry.
by Lisa M May 05, 2006
 
4.
The specific period during the day responsible for decreasing the ability to make good decisions and create coherent, logical statements and/or thoughts. Usually a frequent occurrence that strikes in no specific pattern other than the time at which it occurs. The use of substances usually ensues after the period begins, but the former is not the cause of the latter.
Brian: Hey, so how'd you do on your psych exam this morning?

Justin: Well, I was studying pretty well, and then it hit stupid o'clock...

Brian:Oh, no man...

Chris: Yo, why is the weed gone, and why is "Penis" carved into the wall?

Brian: Are you sure you're just not making excuses for smoking?

Justin: no way, I swear on my life I did it 20 minutes into stupid o'clock!

Brian: I guess... but why "Penis"? Gay.

Justin: ...
by smokebubbles December 19, 2011
 
5.
This is the time of day when one has retired to their place of sleep, to end a tiresome day. When suddenly, they are awoken by a mind boggling thought they had earlier that day. The time when awoken, would be referred to as 'stupid o'clock'.
Michael: " oh no , i forgot what my homework was. I didn't write detailed enough note in my folder."

Stephanie: "you'll think of it at like Stupid O'clock tonight"
by SpanishIrishGuy March 03, 2011
 
6.
Any time before 8 am
I had to get up at stupid o'clock
by Betty February 13, 2004
 
7.
The state of being achieved by remaining awake for extended periods of time. Common symptoms are euphoria, minor delusional behavior, and general silliness.

Distinguishable from sleep deprivation by the lack of paranoia that often accompanies the latter condition.
"We were up til stupid o'clock last night."

(Immediately after someone attempts to stage dive off the sofa onto the coffee table while watching a Madonna video): "Yeah, it's definitely stupid o'clock."
by The Gaunt Man April 12, 2006