IPA: /ˌʌn.bɪˈkʌm.ɪŋ.li/
KK: /ʌnˈbɪkəmɪŋli/
In a way that is not appropriate or suitable; often used to describe behavior that is not fitting for a situation.
She spoke unbecomingly at the formal dinner, which made everyone uncomfortable.
Unbecomingly → It is formed from "un-" (meaning not) and "becoming" (from Old English "becuman", meaning to come or to be suitable) and "-ly" (meaning in a manner). The word "unbecomingly" means in a manner that is not suitable or appropriate.
Think of 'not' ('un-') being combined with 'suitable' ('becoming') to remember that 'unbecomingly' describes behavior that is not appropriate.