The Oxford Thesaurus An A-Z Dictionary of Synonyms - unbecomingadj.

1) unsuited, unsuitable, inappropriate, ill-suited, unfitting, unfit, inapt, unapt, out of character, out of place: It is unbecoming to wear your mink coat to the Save the Animals fund-raising dinner. 2) indecorous, unseemly, indelicate, improper, ungentlemanly, unladylike, offensive, tasteless: Father said it was unbecoming for her to use such foul language.