Like when uttering disbelief at something that happened.
Usually said by crazy people, who imprint it onto the minds of those less fortunate
Beth-checks out Not very fit guy
Rosie- "as if you just checked out that guy, LOL"
Beth- "one day im going to start saying as if"
Beth- "As if sir just made fun of us"
Rosie- "aha i know"
Beth-"holy shit, i said as if"