clandestine, secret or furtive
The backstairs (stairs at the rear of a building).
Crude or unfeeling in manner or speech.
Disagreeably precise or penetrating.
Savagely violent, vicious, ruthless, or cruel.
Harsh; unrelenting.
Direct and without attempt to disguise unpleasantness.
In extreme metal, to describe the speed of the music and the density of riffs.