CSO 

A phrase coined by the UFC's Tony Ferguson, meaning "Champ Shit Only." Implying that he is the true UFC Lightweight champion of the world.

"Where you at McNuggets, you fucking piece of shit, I'm gonna kick your ass! You better come and defend that belt, defend or vacate motherfucker! CSO motherfucker!"

CSO by meatspin.fr May 5, 2020

CSO 

Community Service Officer.
University Employees that provide Escorts and Campus Security. They are often underpaid, overworked and stalked by their clientel.

Can I request an escort from a CSO.
A really cute CSO walked me home last night.

CSO by suptrupe December 28, 2005

CSO 

Completely Sold Out
USUALLY in regards to tickets to a concert of event

I hate it when tickets are CSO early

CSO by MannyFresh September 22, 2005

CSO 

Catholic schoolgirl Outfit

Hope she wears her CSO to the party; that baby rocks!

CSO by SamBeeGees November 9, 2009

CSO 

Complicated Significant Other, for example being friends with someone who rejected you but he's still kinda flirty, etc. There's no other name for your relationship. Can only be used when you're single and he's your or one of your closest things to boyfriend, lover, etc.

"Are you two dating?"
*leans in and whispers*
"he's my CSO I was talking about!"
"Oh!"

CSO by cupcakes3659 December 11, 2016

CSO 

Combined Sewage Event: typically used by public works departments to describe the unintended discharge of large quantities of raw sewage into lakes and oceans. CSO can also be effectively applied to the uncontrollable discharge of large quantities of excrement by an individual.

Where is Bob? He's been gone for over an hour.
He's in the bathroom having a CSO.

CSO by THX1137 July 13, 2010

CSO 

Pronounced ‘See-so’
Stands for ‘Crockery Sanitation Officer’, or ‘dishwasher’ by any other name

I passed my CISSP in 2001! Now I’m a CSO

CSO by Dirk Scab December 12, 2022