When someone jumps on you immediately when you sign in to messenger or another instant messaging application.
I *just* wanted to check my emails and go to bed when Steve IMpounced me and I had to chat for another half hour!
by jbng October 07, 2007
Top Definition
To initiate conversation, the second a person logs into their IM.
X)waiting for sign in
Y)signs in
by Silent0809 February 19, 2009
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