recondite
has been listed 66 times with 3 comments
abstruse
has been listed 62 times with 0 comments
equivocal
has been listed 25 times with 0 comments
cryptic
has been listed 32 times with 0 comments
ambiguous
has been listed 46 times with 2 comments
enigmatic
has been listed 42 times with 0 comments
Don't forget my favorite, ineffable.
inscrutable; incoherent; inchoate; conundrum; arcane?