unspeakable
Concise Oxford English Dictionary © 2008 Oxford University Press:
unspeakable/ʌnˈspiːkəbl/
▶adjective not able to be expressed in words.
■ too bad or horrific to express in words.
– derivatives
unspeakableness noun,
unspeakably adverb.
unspeakableness noun,
unspeakably adverb.
'unspeakable' also found in these Oxford entries:

