When you don't know what to say: there's 2 ways that this is commonly used. One is when someone is sister shooketh and they text respond: sksksksk. The other is when the person just got roasted and they have no response so they just respond "sksksksk" as a form of mockery.
"You're so ugly oh my god."
"That's what ur mom said."
...sksksksk...
*Someone Makes a joke*
SKSKSKSK AND I OOPSKSKSK THAT WAS SOO FUNNY I NEED MY HYDROFLASK AND MY SCRUNCHIES AND I OOP SKSKSK IM SUCH A DUMBASS BITCH SKSKSKSKSK
(So basically sksksks mean ur dumb )