What it means
Online, saying you're screaming means something is so funny or ridiculous that you're reacting with full-volume drama, even if you're actually sat there silent, grinning at your phone. It's a texty, exaggerated way to say you've absolutely lost it laughing.
Usage examples
"He captioned it wrong on purpose and I am screaming."
"Screaming at the way the dog just gave up halfway."
"That typo was so bad I'm screaming."
"She really said that with her whole chest and I'm screaming."
Where it comes from
From scream, the loud cry of shock or delight, hijacked online to mean laughing uncontrollably at something hilarious.
