IPA: /ʌnˈmɛnʧənəbl/
KK: /ʌnˈmɛnʧənəbl/
Something that is not suitable to be talked about or discussed openly.
The topic was so sensitive that it was considered unmentionable in polite conversation.
A thing or topic that is considered too embarrassing or inappropriate to mention or discuss.
The scandal was filled with unmentionables that shocked everyone.
Unmentionable → It is formed from "un-" (meaning not) and "mention" (from Latin "mentio", meaning to refer to or speak of) and the suffix "-able" (meaning capable of being). The word "unmentionable" describes something that is not capable of being mentioned, often due to its taboo nature.
Think of something that is 'not' ('un-') 'spoken of' ('mention') and is 'capable of being' ('-able') avoided in conversation.