Improper Synonyms
Words/phrases that have a similar definition to the word "improper" include...reprehensible, unfitting, irregular, criminal, inadequate, illicit, inappropriate, offensive, indecent, rude, unacceptable, illegal, inopportune, unseemly, crooked, shady, incorrect, not the done thing, dishonest, shocking, unlawful, unsuitable, out of place, wrong
Other words in thesaurus...