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1.
An IM greeting that goes unanswered either because the recipient isn't paying attention or because he/she is ignoring the sender.
Dave sent me an orphaned IM earlier today:

OrphanIM713: hey
OrphanIM713: u going to the party tonight?
OrphanIM713: u there?
OrphanIM713 is away at 1:56 p.m.
by MDL713 September 03, 2005