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Stands for "Sneak In Buddy/Best Goober Friend For Life"; can come in forms of "SIB", "SIBy", or just plain "goob". This is a serious commitment, so only the loyalist and trustworthy of people can join in this grand friendship. Be weary, though, not everyone can handle it.
"Look at that SIBBGFFL go!"
"Awww, SIBy..."
by SIBBGFFL September 27, 2011
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