unmentionable

adj, noun — 2 senses

unmentionable

adj

Etymology From un- + mentionable.

1

Too embarrassing or shocking to be discussed.

Derived terms: unmentionableness, unmentionables, unmentionably

unmentionable

noun

Etymology From un- + mentionable.

1

Something not to be discussed in polite society.

I'm a lesbian female, 20 years old and my most outstanding features are my pierced unmentionable and my eyes.1983 December 10, Mary F. Miller, “Personal advertisement”, in Gay Community News, volume 11, number 21, page 19:
He was taught from childhood that the world does not condone homosexuality and that it is an unmentionable of decent people.1995, Virginia Schroeder Burnham, William H. Hampton, Since Time Began, page 43:

1 more example

Here, after all, was the circle round which Forster passed the manuscript of his novel Maurice which conveyed so much about being 'an unmentionable of the Oscar Wilde sort'.2014, Andrew Hodges, Alan Turing: The Enigma, page 100:

Entry derived from the Wiktionary, under licence CC BY-SA 4.0 — list of authors.