English Etymology From unspeakable + -ness. Noun unspeakableness (uncountable) The condition or quality of being unspeakable. 2007 January 27, Paul Berton, “How do we define gruesome? (editorial)”, in London Free Press, Canada:Obviously, it's the unspeakableness, the sheer horror of it, that is motivating some news organizations. References Oxford English Dictionary, 2nd ed., 1989. See "unspeakable."Wikiwand - on Seamless Wikipedia browsing. On steroids.