SSTTITD stands for Scary Stories To Tell In The Dark, which is a book written by Alvin Schwartz. They're stories you pick up and tell to your friends to scare the crap out of them for the lulz.
Jon: Wanna hear an SSTTITD story?
Joan: SSTTITD?
Jon: Scary Stories To Tell In The Dark...
Joan: NO!! THOSE ARE SCARY!!
Joan: SSTTITD?
Jon: Scary Stories To Tell In The Dark...
Joan: NO!! THOSE ARE SCARY!!
by zachera September 04, 2009
"Scary Stories to Tell in the Dark," Alvin Schwartz's popular collection of frightening American folk stories
On Reddit.com: "Do you remember when you read SStTitD and saw this image for the first time?" accompanied by image of a deteriorating skull
by Milieunaire September 04, 2009