A shameless person does not seem ashamed of bad behaviour, even though other people think they should be. The point is the missing blush: they ask, take, lie, or show off as if nothing were wrong.

even though即使 other people think they should be別人覺得他應該要感到羞愧，a shameless person不要臉的人 does not seem看起來就是不會 ashamed of bad behaviour對自己的不當行為感到羞愧。the point is重點在於 the missing blush少了那份臉紅：they ask, take, lie, or show off他們要東西、拿走東西、說謊、或炫耀，as if nothing were wrong都好像沒事一樣。

It is a strong moral word, and in Chinese the everyday hook is often 不要臉 — not just “no shame” as a quiet fact, but a slap.

and in Chinese而在中文裡 the everyday hook日常最常對應的說法 is often就是 不要臉，it is a strong moral word它是一個語氣很重的道德詞，not just "no shame" as a quiet fact不只是像陳述一個事實一樣說「沒有羞恥心」，but a slap而是像一巴掌。

That said, English also uses it more lightly. A shameless plug is when you advertise yourself without pretending to be modest; a shameless copy is an obvious copy, done without embarrassment. In those phrases the speaker is half joking, half accusing.

that said不過，English also uses it more lightly英文裡這個字也有比較輕鬆的用法：a shameless plug『老王賣瓜』式的自我宣傳 is when you advertise yourself without pretending to be modest指的是你自我宣傳、完全不假裝謙虛；a shameless copy毫不掩飾的抄襲 is an obvious copy, done without embarrassment則是做得毫不害臊、明顯就是抄的。in those phrases用這些說法的時候 the speaker is half joking, half accusing說話者是半開玩笑、半在指責。

The opposite feeling on a face is shamefaced; the opposite judgement of a deed is not quite shameful — a shameful act is one that deserves shame, and a shameless person is one who will not wear that shame. You can be called shameless for the way you refuse to feel it.

the opposite feeling on a face臉上表情的反義詞 is shamefaced是 shamefaced（面帶愧色）；the opposite judgement of a deed但一件事的反義評價 is not quite shameful不完全是 shameful（可恥）——a shameful act is one that deserves shameshameful act（可恥的行為）指的是應該感到羞恥的行為，and a shameless person is one who will not wear that shame而 shameless person 則是不肯揹上那份羞恥的人。you can be called shameless你會被說成 shameless（不要臉） for the way you refuse to feel it就是因為你拒絕去感受那份羞恥。