43 synonyms for inappropriate such as ill-considered, amiss, and ill-advised. Inappropriate is an adjective, and its antonyms are appropriate and suitable.
Amiss, ill-advised, ill-considered, ill-judged, ill-suited, ill-timed, improper, in poor/bad taste, inadvisable, inapposite, inapt, incongruous, indecorous, inexpedient, infelicitous, injudicious, inopportune, lacking in propriety, malapropos, misguided, misplaced, out of keeping, out of order, out of place, regrettable, tactless, tasteless, unbecoming, unbefitting, undesirable, undue, unfit, unfitting, unfortunate, ungentlemanly, unladylike, unprofessional, unseemly, unsuitable, untimely, untoward, and wrong.