A condition that causes somebody to notice the number 420 everywhere.
Though the subject usually doesn't openly associate the occurrences with supernatural or exterior forces (though he may joke about it), there persist at least a doubt or even a strong belief in the his mind that all the occurrences of the number 420 cannot be accidental.
420 delusion:
"Man, it's becoming worse. It's everywhere. I checked the deadline for my application to the University of Tokyo and it was Dec 10, 4:20 pm. Then somebody texts me to tell me the US just won the game against Russia in the Olympics in Sochi and the game just ended: I check the time here: 4:20 am. I google the time in Sochi, Russia: 4:20 pm. I'm telling you, it's a fucking conspiracy."
The act of doing a three hundred sixty degree spin and shooting a target on spot using hip fire on a sniper in any call of duty. 420 simply means the action is done while high on weed.
Yo bro, i cant believe you 420 360 noscoped that dude. Wanna blaze more?
The error message you receive when attempting to connect to the cloud on 4/20.
Billy: It's 4/20, broheim, did you wake and bake?
Becky: NO! Jeff broke the glass bong yesterday, we're all out of papers, and I couldn't find my pipe.
Billy: ooooo 420 error. cloud not found.