unmentionable

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++un·men·tion·a·ble /ʌnˈmenʃənəbəl/ adjective  RUDE/IMPOLITERUDE/OBSCENEtoo shocking or embarrassing to talk about 〔因太震惊或尴尬而〕说不出口的 unmentionable scandals 难以启齿的丑闻

Examples from the Corpus

unmentionable• This behaviour was unmentionable a few years before, although it probably did take place.• Stalin had long been unmentionable and Volkogonov was said to be using closed secret archives.• She hoped she hadn't caught an unmentionable disease from her visit to the news-theatre.• Let us begin with a few simple, crucial, and apparently unmentionable facts about a typical high-school classroom.• Divorce, desertion, and illegitimacy were considered almost unmentionable scandals.• Miguelito yelled up that the man should do something unmentionable to himself.

un·men·tion·a·ble adjectiveChineseSyllable  

or about embarrassing too Corpus talk to shocking

unmentionable
un‧men‧tion‧a‧ble /ʌnˈmenʃənəbəl/ adjective
too shocking or embarrassing to talk about:
    unmentionable scandals

un·men·tion·ableBrE /ʌnˈmenʃənəbl/ 🔊NAmE /ʌnˈmenʃənəbl/ 🔊 adjective [usually before noun] too shocking or embarrassing to be mentioned or spoken about 不可提及的；不宜述说的；难以启齿的◆an unmentionable disease羞于启齿的疾病