What Is A "Basement Slab" Or A Basement Slabber"?

I have seen the following slabbers before: NNC, NTC, and ICG

But a recent auction search turned up these new ones:
PCC, CGGA, and HCGS

"A basement slabber slabs his own coins in Coin World slabs or some other type of crude holder, sticks on a sketchy label printed out of a low-quality printer, printed with an amazingly high grade for the coin it describes, and sells on ebay for ridiculously high prices for unaware beginning numismatists."

That was describing me right up to the word 'printer'.

I'm slabbing all my coins in Coin World holders, but not putting a grade on the label. Nor selling them, at least not now.