Words

oracular

(of an utterance, advice, etc.) hard to interpret; enigmatic 

Delphic

deliberately obscure or ambiguous(relating to the ancient Greek oracle at Delphi)

esoteric

intended for or likely to be understood by only a small number of people with a specialized knowledge or interest

recherché

rare, exotic, or obscure

arcane

understood by few; mysterious or secret

recondite

(of a subject or knowledge) little known; abstruse

abstruse

difficult to understand; obscure

obscure

not clearly expressed or easily understood

inscrutable

impossible to understand or interpret

impenetrable

impossible to understand

incomprehensible

not able to be understood; not intelligible

equivocal

open to more than one interpretation; ambiguous 

ambiguous

open to more than one interpretation; not having one obvious meaningnot clear or decided 

gnomic

difficult to understand because enigmatic or ambiguous:

paradoxical

seemingly absurd or self-contradictory

laissez-faire 

the policy of leaving things to take their own course, without interfering