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A self invite, or SI, occurs when someone decides to invite themselves into an activity to which they were not explicitly invited.

An "epic SI" is a derivative of the SI, where this person continues to invite themselves after being explicitly told "you are NOT invited".

Very frequently, this type of social ineptitude leads to being labeled your dawg in jest.
Mich showed up at my Super Bowl party and ate all the chips. I didn't invite him, so he self invited himself!
by moraleboatanchor March 24, 2013