IMPROPER Meaning of IMPROPER in English a. 1.Unsuitable, unsuited, unfit, unapt, inapposite, inappropriate, unadapted, not proper.2.Unseemly, unbecoming, indecent, indecorous.3.Inaccurate, incorrect, erroneous, wrong. Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012