elusive

Adjective

Synonyms: subtle baffling knotty problematic problematical tough

WordNet 3.0

Adjective (4)

difficult to describe“a haunting elusive odor”
skillful at eluding capture“a cabal of conspirators, each more elusive than the archterrorist — David Kline”
difficult to detect or grasp by the mind or analyze“his whole attitude had undergone a subtle change”“a subtle difference”“that elusive thing the soul”Synonyms: subtle
making great mental demands; hard to comprehend or solve or believe“a baffling problem”“I faced the knotty problem of what to have for breakfast”“a problematic situation at home”Synonyms: baffling knotty problematic problematical tough

Webster's Dictionary (GCIDE)

Elusive \E*lu"sive\, a. Tending to elude; using arts or deception to escape; adroitly escaping or evading; eluding the grasp; fallacious. [1913 Webster]

Elusive of the bridal day, she gives Fond hopes to all, and all with hopes deceives. --Pope. -- E*lu"sive*ly, adv. -- E*lu"sive*ness, n. [1913 Webster]