1 immutable changeless, invariable, unalterable, unchanging, undeviating
alterable, changing, inconsistent, vacillatory, varying
2 impervious impassable, impenetrable, impermeable, inaccessible
accessible, enterable, passable, penetrable, perforable, porous
3 implacable - grim, merciless, relentless, unappeasable, unpacifiable, unrelenting
appeasable, clement, compassionate, conciliatory, merciful, reconcilable
4 incongruous discordant, discrepant, incompatible, inconsistent, inconstant, uncongenial
appropriate, compatible, congruous, consistent, fitting, suitable
5 indolent lazy, otiose, slothful, unindustrious,
assiduous, busy, diligent, industrious, sedulous
6 infallible flawless, impeccable, inerrable, inerrant, unerring
errable, errant, fallible, imperfect
7 infirm decrepit, frail, inconstant, irresolute, vacillating,
hale, healthy, vigorous, resolute, steadfast unwavering
8 innocuous innocent, inoffensive, unoffending
harmful, pernicious
9 insatiate gluttonous, unappeasable, unquenchable, unsated, unsatisfied
gratified, quenched, sated, satisfied, sufficed
10 inscrutable arcane, impenetrable, inexplicable, mysterious, unknowable
comprehensible, intelligible, penetrable, perceivable, perspicuous
11 insensate callous, dispassionate, insensitive, unaffected, unfeeling, unmoved
compassionate, empathetic, responsive, sensitive, tender-hearted
12 irrelevant extraneous, immaterial, inapplicable, inconsequent, unconnected, unrelated
applicable, germane, pertaining, pertinent, related