Not to be confused with the literal and anatomical definition of 'bone'.
The term stems from the use of 'bone' as synonymous to the action of 'hooking-up' or 'having sex'. Thus a 'bone-bud' is someone you are currently hooking-up with, and is a term synonymous to a 'friend with benefits'.
Hey, did you hear about those two? Since that party last weekend, they're now bone-buds.
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