na-adjective
extremely rude; outrageously impolite
A strong yojijukugo used to condemn behavior that is shockingly disrespectful or impertinent. Often used in formal or written contexts.
彼の態度は無礼千万だ。
His attitude is extremely rude.
そんな要求をするとは無礼千万な話だ。
Making such a demand is outrageously impolite.
A yojijukugo combining 無礼 (rudeness) and 千万 (extremely, myriad). The exact historical derivation is uncertain, but it follows a common pattern of intensifying a quality with 千万.