tenebrous (adj.)

• ambiguous
• black
• caliginous
• dark
• darkling
• dim
• dusky
• ebon
• ebony
• equivocal
• gloomy
• murky
• obscure
• pitch-black
• pitch-dark
• pitchy
• rayless
• sibylline
• starless
• sunless
• tenebrious
• uncertain
• unclear
• unilluminated
• unintelligible
• unlighted
• unlit
• vague