So shocking, rude, or embarrassing that people will not say it out loud. It is used of subjects rather than of single words — death in some families, money in others, an illness nobody names, a relative everyone has agreed to forget.

So shocking, rude, or embarrassing太令人震驚、太失禮或太尷尬 that people will not say it out loud讓人不會把它說出口。It is used of subjects這個字用在話題上 rather than of single words而不是單一的字詞上——death in some families在有些家庭裡是死亡, money in others在有些家庭裡是錢, an illness nobody names是沒有人肯講出名字的一種病, a relative everyone has agreed to forget是大家說好要忘記的一個親戚。

What makes the word interesting is that it is almost never a plain report; the speaker is usually half-smiling at the silence. When an English speaker says 'we never discussed the unmentionable subject of Grandfather's first wife', the taboo is being described and gently mocked at the same time.

What makes the word interesting讓這個字有趣的地方 is that it is almost never a plain report在於它幾乎從來不是平鋪直敘的陳述; the speaker is usually half-smiling at the silence說話的人通常是半笑著在講那個沉默。When an English speaker says當英文使用者說 'we never discussed the unmentionable subject of Grandfather's first wife'『我們從來沒討論過爺爺第一任太太這個不能提的話題』, the taboo is being described這個禁忌被講出來了 and gently mocked at the same time同時也被輕輕調侃了一下。

Used with a completely straight face, it belongs to older or more formal writing.

Used with a completely straight face如果用完全一本正經的表情講, it belongs to那就是屬於 older比較舊式的 or more formal writing或比較正式的寫作。

There is a real difference between 'unmentionable' and 'unspeakable': unspeakable means so terrible that words fail — unspeakable cruelty — while unmentionable means merely not allowed in polite conversation. One is horror, the other is manners.

There is a real difference有一個真正的差別 between 'unmentionable' and 'unspeakable'在 'unmentionable' 和 'unspeakable' 之間: unspeakable meansunspeakable 的意思是 so terrible that words fail太可怕了，講不出話來——unspeakable cruelty像 unspeakable cruelty（駭人的殘忍）——while unmentionable means而 unmentionable 的意思只是 merely not allowed in polite conversation在有禮貌的談話裡不能提。One is horror一個是恐怖, the other is manners另一個是禮貌。

It also works as a noun for the thing itself, though that is rare in the singular; the plural has a life of its own and is listed separately.

It also works as a noun它也可以當名詞用 for the thing itself指那件事本身, though that is rare in the singular不過單數形式很少見; the plural has a life of its own複數形式自己有另一套用法 and is listed separately所以另外列出來。