Synonyms for Inappropriate:

adj.

extraneous (adjective)
eerie, alien, segregated, extraneous, foreign, estranged, outside, irrelevant, exotic, inapplicable, foreign-born, parenthetical, detached, Unallied, unessential, unaffiliated, outer, other, inadmissible, immaterial, external, removed, inapposite, outlandish, separate, disaffiliated, disjoint, dissociated, strange, extrinsic, separated, nonessential, impertinent, extraterrestrial, disconnected, unrelated.
improper (adjective)
un, unseemly, unbefitting, Unapt, improper, unfit, indelicate, untoward, MLY, indecorous, unsuitable, indecent.
inappropriate (adjective)
unbefitting, malapropos, unfit, of place, unbecoming, unsuited, inapt, out, unsuitable, inapposite, ill-matched, improper.
inopportune (adjective)
inauspicious, inopportune, awkward, inconvenient, belated, untimely, delinquent, inexpedient, infelicitous, unpunctual.
not proper, suitable (adjective)
improper, unfitting, indecorous, unbefitting, inapplicable, untimely, unfit, incorrect, irrelevant, inept, wrong, unseemly, incongruous, unbecoming, ill-suited, malapropos, unsuitable.
unacceptable (adjective)
insufficient, unsuitable, deficient, intolerable, inadequate, inadmissible, inferior, unacceptable, unsatisfactory, untenable.
wrong (adjective)
incorrect.

n.

discourteous, offensive, impudent, insolent, smart, abrasive, rude, impolite, ill-mannered. usual, Unapt, agree, inept. ill-suited, ability. inappropriate (noun)
incompatible, unfitting, out or keeping, unbefitting, wrong, improper, unsuitable, incorrect, incongruous.

Other synonyms:

Unapt, ill-chosen. ill-suited. unhappy. unfortunate. boorish
rude.
unsuitable
inept.
Other relevant words:
un, incorrect, rude, smart, impudent, ill-mannered, incompatible, ability, insolent, inept, impolite, incongruous, abrasive, discourteous, usual, offensive, Unapt, agree, unfortunate, ill-chosen, unfitting, wrong, unhappy, ill-suited, MLY.