1 wrong, mistaken, erroneous, false, incorrect, inaccurate, inexact, imprecise, amiss, faulty, untrue, irregular, abnormal:
Sloppy research had led to improper conclusions.
2 unfit, unsuitable, inappropriate, inapt, inapplicable, infelicitous, incongruous, unsuited, unseemly, unbefitting, unfitting, uncalled-for, inapposite, malapropos, out of keeping, out of place, incompatible, inopportune:
Do you think it improper for shops to open on Sundays? His wedding was an improper occasion for comments about his philandering.
3 indecorous, indecent, indelicate, immodest, unseemly, untoward, unbecoming, impolite, suggestive, risqué, off colour, obscene, corrupt, immoral, sinful, wicked, lewd, lascivious:
Do you see anything improper in sex education for children?