WTS

“What the sigma” is a term used in slang. It’s a version of “what the fuck/hell/heck”. A sigma is a cool dude or alpha. Also used is the term “erm, what the sigma”. These phases were popularized by a popular video of squidward from SpongeBob SquarePants saying “erm, what the sigma”. What the sigma is also used as a sound effect

John: “Bro, guess what! I found my mom on a dating app!”

Bob: “erm what the sigma (aka WTS)
(In this case, bob is using “what the sigma” as a replacement for “what the fuck/hell/heck”)

Poppy: *says something out of pocket/weird*
Emma: “what the sigma (aka WTS)”
(Same case)