Slang for "celibate," aka, refraining from sexual activity.
Chad: Yo, when was the last time you hooked up with Becca?
Brad: I dunno, like a month maybe?
Chad: Daaaamn bruh, maybe she went celly.
Short for INCEL meaning a boy or man unable to sexually attract a girl of woman into a relationship due to the being unattractive or unlikable. CELLI is almost always used as an INSULT however do not have hostile views against women.
Wow look at that guy what a CELLI