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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
 
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