SD is an abbreviation for Sneak Dissers, meaning people who talk behind your back or whatever.
"Ayo there's that fuckin SD"
"Huh?"
"Sneak Disser"
Basically a term for rage quit, but commonly for games like Super Smash Bros. You basically either gave up because someone else is better at the game, or you sacrificed yourself to kill someone else in-game.
"Dude, why did you SD?"
"You're being an asshole to the other gamers and I don't want to deal with that bs."
"Dude...It's just a game. You just lost the game because you're being stupid."
"Whatever."
SD&L the meaning of Suck Dick And Live!
It just means live life to the fullest.
Hey Bro! SD&L
Hey girl Just SD&L.
SUCK DICK AND LIVE!
Peaky SD (or PKSD in short) The polar opposite of PTSD, instead of having reocurring memories of traumatic events, you instead recall moments that are "peak" (very good).
"Dude... I just got Peaky SD"
"From what?"
"I just recalled my Balatro run..."
"Stop crying; start dying!"
From the Killwhitneydead song title, "Stop Crying Just Stop Dying," a rude way to tell someone to shut up or stop complaining.
"You're such a jerk to not give us a ride!"
"But I haven't had my license for a year yet... you know what, 'SC/SD!'"
"They've been sucking him so hard and long, they got SDS after taking it up the brown hole!"