1.Definition: defying expression or description
Related Adjective(s):indefinable, indescribable, ineffable, untellable, unutterable
2.Definition: exceptionally bad or displeasing
"An unspeakable odor came sweeping into the room"
Related Adjective(s):abominable, atrocious, awful, dreadful, painful, terrible
3.Definition: too sacred to be uttered
Related Adjective(s):ineffable, unnameable, unutterable