IPA: //ˌʌn.bɪˈkʌm.ɪŋ.nəs//
KK: /ʌnˈbɪkəmɪŋnəs/
A state of being inappropriate or not suitable for a particular situation; it refers to behavior or appearance that is not fitting or proper.
Her unbecomingness at the formal event drew disapproving looks from the guests.
Unbecomingness → It is formed from "un-" (meaning not) and "becoming" (from Old English "becuman", meaning to come or to be suitable) and the suffix "-ness" (meaning the state or quality of). The word refers to the state of not being suitable or appropriate.
Think of 'not' ('un-') being suitable or appropriate ('becoming') — that's why unbecomingness means the quality of being unsuitable.