im·prop·er adj: not proper: asa: not in accord with correct procedurean improper venueb: wrongful; specif: in violation of a constitutionthe denial of trial by jury was held improperim·prop·er·ly adv
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.
amiss, awkward, contrary to decency, contrary to good taste, discordant, discrepant, erroneous, false, forbidden, gross, ill-adapted, ill-founded, ill-timed, illicit, illogical, immodest, immoral, inaccurate, inadmissible, inapplicable, inapposite, inappropriate, inapt, incongruous, incorrect, indecent, indecorous, indecorus, indelicate, indignus, inept, inexact, infelicitous, inharmonious, inopportune, irrelevant, mistaken, naughty, not pertinent, not right, not suitable, objectionable, off-color, off the mark, out of place, prohibited, risque, unadapted, unallowable, unauthorized, unbecoming, unbefitting, uncharacteristic, undesirable, undue, unfit, unfitting, unmeet, unreasonable, unrefined, unseasonable, unseemly, unsound, unsuitable, unsuited, untimely, unwarrantable, wide of the mark, wrong, wrongful
associated concepts: improper act, improper conduct, improper discharge, improper influence, improper joinder of actions, improper motive, improper performance, improper practice, improper use
bad (offensive), blatant (obtrusive), culpable, delinquent (guilty of a misdeed), disgraceful, disorderly, disreputable, drastic, false (inaccurate), faulty, illegal, illegitimate (illegal), illicit, immoral, impertinent (insolent), inaccurate, inadmissible, inapplicable, inapposite, inappropriate, inapt, incongruous, incorrect, inelegant, ineligible, inept (inappropriate), iniquitous, lascivious, nefarious, objectionable, perverse, profane, slipshod, suggestive (risqué), unauthorized, unbecoming, undesirable, undue (excessive), unfit, unjust, unprofessional, unseemly, unsuitable, untimely, unwarranted, vicious, wrongful
Burton's Legal Thesaurus. William C. Burton. 2006