It is derived from: "I do not know"
It was changed to: "I don't know"
Then: "I Dunno"
Finally: "Iunno"
"When did that happen!?"
"Uh.... Iunno."
by Kavkid June 2, 2006
another way of saying "i don't know"
often used in online chatting
by frank meng July 18, 2003
"I dont know", but really fast.
Usually AIM slang.
lkdsf0990 : "what did you do today?"

kjdsfh900: "iunno."
by doodooheadnicole October 9, 2005
It is derived from: "I do not know"
It was changed to: "I don't know"
Then: "I Dunno"
Finally: "Iunno"
"When did that happen!?"
"Uh.... Iunno."
by Kavkid June 2, 2006
a word used in conversation when the person is severly bored and uninterested in the current discussion. usually used by those who are lazy and fatigued.
Tim: dude, what topic are you choosing for your english essay?
Jack: iunno
Tim: dont you have any ideas at all?
Jack: iunno!!
by ribeco !! June 10, 2008