a)
Literally: The pubic hairs around the
butt. See: buttfluff
b) Figuratively: Style without substance, frivolous, useless, meaningless, unintelligent, pointless, form lacking function, redundant, annoying, irritating.
The Prisoner remake was pure
butt fluff. Go watch the original if you have a brain.
That
girl is
hot but she's got nothing but butt fluff between her ears.