destitute or deprived of sensation; unconscious.

lacking mental perception, appreciation, or comprehension.

stupid or foolish, as persons or actions.

nonsensical or meaningless, as words

This letter is either cryptic or senseless.

noun

absurdity , folly , foolery , idiocy , imbecility , insanity , lunacy , madness , nonsense , preposterousness , silliness , tomfoolery , zaniness