na-adjective, noun
bad form; indecency; impropriety
Describes behavior, appearance, or writing that is improper, indecent, or lacking in good manners. Often used in formal or critical contexts.
彼の服装は不体裁だった。
His attire was improper.
会議での発言は不体裁だと批判された。
His remarks at the meeting were criticized as indecent.
無作法 is a more common synonym for rudeness or ill manners, whereas 不体裁 is less frequent and carries a stronger nuance of impropriety.
Compound of 不 (fu, 'not') and 体裁 (teisai, 'appearance, form, decency'). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for negation.