extremely rude; outrageously impolite
A strong yojijukugo used to condemn behavior that is shockingly disrespectful or impertinent. Often used in formal or written contexts.
His attitude is extremely rude.
Making such a demand is outrageously impolite.
失礼 is a general term for rudeness or impoliteness, while 無礼千万 is a much stronger, emphatic expression reserved for extreme cases.
無礼 means 'rudeness' or 'impoliteness', but 無礼千万 intensifies it to 'extremely rude'.
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.