indefinite

abysmal

countless, incalculable, incomputable, inestimable, innumerable, unmeasured

exhaustless, inexhaustible

extensive, far-flung, immense, vast

ambiguous, cryptic, dark, enigmatic (also enigmatical), equivocal, murky, nebulous, obscure, unintelligible

bleary, blurry, dim, faint, foggy, gauzy, hazy, misty, woozy

indeterminate, indistinct, indistinguishable, uncertain, undefinable, undefined, undetermined

inexplicable, inscrutable, mysterious

baffling, bewildering, confounding, confusing, mystifying, obfuscatory, perplexing, puzzling, unfathomable

dark, dusky, gloomy

impalpable, inappreciable, intangible, invisible

hieroglyphic (also hieroglyphical), incomprehensible, indecipherable, indiscernible, inexplicable, mysterious, obfuscatory, puzzling