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.