spim

from The Free On-line Dictionary of Computing (8 July 2008)
spim

   <messaging> (From {spam} and {IM}) Unsolicited commercial
   messages sent via an {instant messaging} system, instant
   messenger spam.

   (2008-01-21)
from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)
SPIM
       SPAM over Instant Messaging (SPAM, IM)
antiflux / dictionary / spim
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