Top Definition
One of the four Galilean moons of Jupiter, so called because of being discovered by Galileo. The most volcanically active object in the Solar system.
Hey, look in my telescope: you can see Io, Europa, Ganymede, and Callisto.
by antinous February 02, 2004
Acronym for Irrelevant One
Kimmie nicknamed herself IO after falling for Ben's crap for time one hundred. I hate to agree but he sure doesn't seem to care much about her feelings.
by Shyantha December 20, 2006

Instant Orgasm, used by girls to describe something they find attractive and or hot.
"Wow! that sports car is cool." "Yeah! its a total IO."
by aussieslang101 November 11, 2009
Acronym (Slang) for "I'm Out" when conversing using the Microsoft Communicator Software. v. The act of hastily departing an online collaboration session with little notice to others participating in the dialogue.

I am no longer part of this conversation as it is digressing rapidly; it will inevitably over-step that invisible moral line in the sand that uniquely distinguishes the employed from the homeless.
"Dude, I wanna dip it in the new workstudy sittin in the corner desk..."
<end of converstion>
by Big G Funk November 03, 2008
A british* acronym for instead of.
The lecture is on Tue io Thu.

OR (it may be used with dots)

I bought some bananas i.o. apples.
by veekadikoydegskupayialiyor December 31, 2012
Free Daily Email

Type your email address below to get our free Urban Word of the Day every morning!

Emails are sent from We'll never spam you.