extremely insolent; outrageously audacious; reprehensible
A strong, emphatic yojijukugo used to condemn behavior as utterly lawless, shameless, or beyond the pale. Often found in formal or literary contexts.
Even I was angered by his utterly insolent attitude.
その政治家の不埒千万な発言は、多くの批判を浴びた。
The politician's outrageously audacious remarks drew widespread criticism.
不埒 means 'lawless' or 'insolent' on its own, while 不埒千万 intensifies it to 'extremely insolent' or 'utterly outrageous'.
言語道断 also expresses strong condemnation, but focuses more on something being unspeakably bad or preposterous, whereas 不埒千万 emphasizes brazen insolence or lawlessness.
A yojijukugo combining 不埒 (lawless, insolent) with 千万 (extremely, myriad) to form an emphatic expression meaning 'utterly insolent' or 'extremely audacious'.