What is Sidebuster?
1.
somebody who always tries to include themself in a conversation.
that fool joe is a sidebuster.
2.
A sidebuster could also mean someone who is fake or phony portraying to be cool.
that fool joe is a sidebuster.
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3.
Someone who in gets in to other peoples conversations without being directly acknowledged or asked for an interjection of some sort.
I'm about to smack the shit out of this Sidebuster!
See