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1.
"IBRN" is a shortcut of saying I'm Busy Right Now.
Used by people in games who are attacking a boss and they are too into it to type "I'm but right now" so they just type "IBRN".
<john> Dude! Can you lyke helping me with thisss????!??
<mark> IBRN
<john> oh you must be facing a strong monster, good luck!
by Dx619 January 21, 2008