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1.
When you stay up until around 3am or more in the morning and can't think straight and saying random things.
It was 4am in the morning and I was on a nighttime high so I started saying random stuff.
by Zongy January 05, 2009
 
2.
a state of mind in which you are so deprived of sleep that you attain a feeling of high much like marajuana.
Resulting in, but not limited to; thinking everything is excesively hilarious when in reality it is not or, acting like an idiot while half way between sleep and awake.
"It's 5 in the morning and brent just tried to jump off the roof, that guy must have a serious night-time high to pull that crazy shit!!"
by TheChosenOne599 June 30, 2009