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1.
y/o
abbreviation for 'year old'
...the most dumbest 17 y/o you ever heard :)
by teh nazi | cheesecake April 21, 2006
 
2.
y/o
It's how Minnesotas abbreviate YOU/KNOW cuz they say it over 50 times a minute
"He's the perfect face of Ryan Reynolds, y/o that?"
"You betcha!"
by Moonrockraindance January 11, 2012
 
3.
y/o
Dual conjunction to replace the term "and/or".

Etymology: Spanish origin.
Your heart is black y/o shriveled.
by A Like the Fonz May 16, 2008