IPA: //ˌʌn.bɪˈsiː.mɪŋ//
KK: /ʌnˈbisiːmɪŋ/
Not suitable or appropriate for a particular situation; lacking in proper decorum or manners.
Her loud laughter at the serious meeting was considered unbeseeming by her colleagues.
Unbeseeming → It is formed from "un-" (meaning not) and "beseeming" (from Old English "beseon", meaning to seem or appear). The word "unbeseeming" means not appearing appropriate or fitting.
Think of 'not' ('un-') appearing or seeming appropriate ('beseeming') — that's why unbeseeming means something that does not seem fitting.