Almost always refers to a song that was initially
trance or
dubstep, sped up to the point where the lyrics sound like they are being recited by a hurried chipmunk, featuring a strong beat which is is audible but barely discernible. The song is then posted on YouTube, usually giving no credit to its initial creator, accompanied by a visual of an
anime girl (or multiple anime girls).
"Back in my day we used to play 45RPM records at 78RPM just for
shits and giggles, but nobody ever called it nightcore."
"I used to listen to music while I was on speed, but now I quit the speed and just listen to nightcore instead."
