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1.
Similar to BFF, but refers to someone who you have been best friends with since kindergarten, hence the acronym "BBSK" means "best bud since kindergarten". Coined by Ryan Laserbeam (played by Matt Shively), in reference to his best friend True Jackson (played by Keke Palmer) on "True Jackson, VP".
Hey guys, you have gotta meet my awesome bud Doug sometime. He's my BBSK.
by tmanokc June 22, 2010
 
2.
Best Bud Since Kindergarden
"You have to take me! I'm your BBSK!"
by Artsygal February 13, 2010