Not easily solved:
— An apparantly insolvable problem.

synonyms: unresolvable, unsoluble, unsolvable.

Roget 519: unintelligible, unaccountable, undecipherable, undiscoverable, unknowable, unfathomable; incognizable^†, inexplicable, inscrutable; inapprehensible^†, incomprehensible; insolvable^†, insoluble; impenetrable.    illegible, as Greek to one, unexplained, paradoxical; enigmatic, enigmatical, puzzling (secret) 533; indecipherable.    obscure, dark, muddy, clear as mud, seen through a mist, dim, nebulous, shrouded in mystery; opaque, dense; undiscernible etc. (invisible) 447^†; misty etc. (opaque) 426; hidden etc. 528; latent etc. 526.    indefinite, garbled etc. (indistinct) 447; perplexed etc. (confused) 59; undetermined, vague, loose, ambiguous; mysterious; mystic, mystical; acroamatic^†, acroamatical^†; metempirical; transcendental; occult, recondite, abstruse, crabbed.    inconceivable, inconceptible^†; searchless^†; above comprehension, beyond comprehension, past comprehension; beyond one's depth; unconceived.    inexpressible, undefinable, incommunicable.    unpredictable, unforeseeable.    ... show more

Polish: nierozwiązalny