Difficult to describe.

Roget 545: deceived etc. v.; deceiving &c.; cunning etc. 702; prestigious^†, prestigiatory^†; deceptive, deceptious^†; deceitful, covinous^†; delusive, delusory; illusive, illusory; elusive, insidious, ad captandum vulgus [Lat.].    untrue etc. 546; mock, sham, make-believe, counterfeit, snide [Slang], pseudo, spurious, supposititious, so-called, pretended, feigned, trumped up, bogus, scamped, fraudulent, tricky, factitious bastard; surreptitious, illegitimate, contraband, adulterated, sophisticated; unsound, rotten at the core; colorable; disguised; meretricious, tinsel, pinchbeck, plated; catchpenny; Brummagem.    artificial, synthetic, ersatz [G.]; simulated etc. 544.    ... show more

Roget 623: unsought, unattempted; avoiding etc. v.; neutral, shy of etc. (unwilling) 603; elusive, evasive; fugitive, runaway; shy, wild.    ... show more

Roget 773: violating etc. v.; lawless, transgressive; elusive, evasive.    unfulfilled etc. (fulfill) etc. 772.   

Skillful at eluding capture.

Difficult to detect or grasp by the mind or analyze:
— That elusive thing the soul.

synonym: subtle.

Making great mental demands; hard to comprehend or solve or believe.

synonyms: baffling, knotty, problematic, problematical, tough.

Polish: problematyczny