TNBM 

True Norwegian Black Metal.
Using full-length name when pronounced.)
Known to be the tr00 name of the tr00 bands of second-wave black metal (Norwegian Black Metal).
Bands that are TNBM: Mayhem, Burzum, Darkthrone, Immortal, Gorgoroth, Satyricon, Emperor, Enslaved, Windir ++

Bands like Dimmu Borgir (Demon Burger) is NOT TNBM, but

"I prefer TNBM, like Mayhem and Burzum. Hail!"

TNBM by Killehrpanda April 20, 2007