You Only Senior Once - an expression used by both seniors in high school and seniors in college as an excuse to do something stupid or crazy. It's similar to "YOLO", but is reserved solely for the use of seniors.
"I didn't study for any of my finals, I was out partying all weekend. Whatever... YOSO!"
You Only Stick Once. The process of hitting on multiple people knowing that you will at least hook up with one of them. The genesis of this acronym comes from the expression, "Throw enough shit against the wall and something is bound to stick."
I justtinder messaged 50 girls. At least one of them is going to be down. #yoso
You only slide once. Termed for when you go on waterslides at waterparks and perform dangerous stunts and tricks on them. This usually occurs on rather large slides, with quite a bit of height.
"Jack is about to go down that giant waterslide while standing up!"
"YOSO, Jack! YOSO!"
The love child of "yo" and "so". Used to catch a peer's attention when one is about to say something important. Often capitalized when the shock factor of what the speaker is saying exceeds lowercase letters, becoming YOSO! When one is expressing concern or wary, they might draw the letters out to resemble "yooooossooooo". Derived from the popular comedy duo Jake and Amir. May also be used as a greeting between two friends.
Nicole: Yoso my cat threw up in the bong water.
Diana: Ugh, tits.
or
Amir: Yoso, when it snows my feet, they bleed coz my shoes have holes and I can nay afford socks'o.
or
Randall: YOSO PARTY AT MY PLACE TONIGHT!
or
Friend #1: Yoso
Friend#2: Yooosoooo I have a test tomorrow and I'm not ready!