The act of releasing anal gas with no underwear on, with such pressure that any residue (poo flakes) left behind on the anus after poo-ing are released into the air.
"I let rip a massive bare bum flaker getting up this morning, you could almost chew the air!"

"I got the bitch back last night by bare bum flaking her in the face while she slept"
by LittleMissFlaker March 17, 2013
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