artful
difficult
hard
impalpable
unidentifiable
baffling
cagey
elusory
evanescent
evasive
fallacious
fleeting
fugitive
imponderable
incomprehensible
indefinable
insubstantial
intangible
malingering
mysterious
phantom
shifty
shirking
slippery
transitory
tricky
alluring
compel
disturb
ethereal
exotic
obscure
shadowy
subtle
unreal
vague
vivid
abusive
allusive
collusive
conclusive
conducive
exclusive
illusive
inclusive
inconclusive
intrusive
nonexclusive
obtrusive
reclusive
unobtrusive