A dead tune is a tune that is so bad the amount of positive emotion showed while listening to it is so bad that you may as well be dead and/or want to be dead.
When someone is completely deader than dead. Not like you're dead dead, but like you're DEAD DEAD. No respawn, but dead, straight DEAD like a bag of bones.
Joel got booty tickled so damn hard, he dead as bones my fellow n word.
A dead meme is a meme that was discovered by normies and thus gets overused to the point it loses its original charm and becomes a husk of its former self.
Not all normie memes are dead memes. Some memes were always normie, like minion memes.
Using a dead meme is very disrespectful to the meme's spirit, so it is recommended to not use dead memes.