1. Short for Phantasy Star Online
2. An addicting drug that is taken through the eyes, highly addictive in large doses, smaller doses cause intrigue

when you're hungover as shit after a spending a night drunk as a skunk

PSOS stands for 'purple shirt of sex' and is a reference to the purple button up shirt Benedict Cumberbatch wears in BBC Sherlock.

A great game avalible on DC, GC and Xbox.

I love it. Can't wait for episode 3.

PSO stands for Phone Sex Operator and is a person who will engage in phone sex in exchange for money.

Potential Significant Other, referring to an individual not quite your significant other. Could pertain to a date, a crush, an unrequited lover, a stranger you'd like to marry, etc.

PSO Perfect Shitting Opportunity