indistinct, vague, ambiguous, indeterminate, indefinite, enigmatic, cryptic, equivocal, unintelligible, impenetrable, inscrutable, unfathomable, unclear, insoluble, involved, uncertain, indecisive, undefined, intricate, illegible, incomprehensible, hazy, dark, dim, abstruse, unaccountable, inexplicable, inconceivable, complicated, illogical, imprecise, unreasoned, mixed up, doubtful, questionable, dubious, inexact, unreasoned, loose, ill-defined, unidentified, invisible, undisclosed, perplexing, escaping notice, mystical, veiled, secret, concealed, mysterious, recondite, esoteric, puzzling, confusing, confused, difficult, complex, lacking clarity, unreadable, contradictory, wanting precision, in need of clarifying, out of focus, in need of translation, murky, clear as mud*, too much for*, over one's head*, deep*, far out*; see also complex 2, confused 2, confusing, difficult 2, uncertain 2, vague 2.
unknown, rare, hidden, covered, remote, removed, retired, reticent, secretive, seldom seen, unseen, inconspicuous, humble, invisible, abstruse, mysterious, deep, cryptic, oracular, enigmatic, esoteric, arcane, undisclosed, cabalistic, inexpressible, unapprehended, dark; see also distant 1, irrelevant, profound 2, secret 1.
obscure applies to that which is perceived with difficulty either because it is concealed or veiled or because of obtuseness in the perceiver their reasons remain obscure; vague implies such a lack of precision or exactness as to be indistinct or unclear a vague foreboding; enigmatic and cryptic are used of that which baffles or perplexes, the latter word implying deliberate intention to puzzle an enigmatic smile, a cryptic warning; ambiguous applies to that which puzzles because it allows of more than one interpretation an ambiguous title; equivocal is used of something ambiguous that is deliberately used to mislead or confuse an equivocal answer
Deficient in brightness:caliginous, dark, dim, dusky, murky. See light
Not clearly perceived or perceptible:blear, bleary, cloudy, dim, faint, foggy, fuzzy, hazy, indefinite, indistinct, misty, shadowy, unclear, undistinct, vague. See clear
Far from centers of human population:back, insular, isolated, lonely, lonesome, outlying, out-of-the-way, remote, removed, secluded, solitary. Idiom: off the beaten path (or track). See near
Not readily noticed or seen:inconspicuous, unconspicuous, unnoticeable, unobtrusive. Idiom: having (or keeping) a low profile. See see
Not known or not widely known by name:nameless, unheard-of, unknown. See knowledge
Liable to more than one interpretation:ambiguous, cloudy, equivocal, inexplicit, nebulous, uncertain, unclear, vague. See certain, clear
To make dim or indistinct:becloud, bedim, befog, blear, blur, cloud, dim, dull, eclipse, fog, gloom, mist, obfuscate, overcast, overshadow, shadow. See clear
To conceal in obscurity:hide1, submerge. See show
To cut off from sight:block (out), conceal, hide1, obstruct, screen, shroud, shut off (or out). See show