(a.) Incapable of being adequately described; inexpressibly bad; unutterable; as, unspeakable grief or rage\.

abominable abusive appalling arrant atrocious awesome awful backhand backhanded bad baneful base beastly black blamable blameworthy calumnious contumelious criminal damnable dark degrading detestable dire disgraceful disgusting distasteful divine dreadful evil exceptional execrable extraordinary fabulous flagitious flagrant foul grim hateful heavenly heinous hideous holy horrendous horrible horrid horrific horrifying humiliating improper incommunicable indefinable indescribable ineffable inenarrable inexpressible infamous iniquitous innominable insolent insulting inviolable inviolate knavish left-handed legendary loathsome low marvelous monstrous mythical naughty nefarious noncommunicable noteworthy numinous obnoxious odious offensive outrageous peccant phenomenal portentous prodigious rank religious remarkable repellent reprehensible reprobate repugnant repulsive revolting rotten sacred sacrosanct scandalous scurrile scurrilous shameful shocking sinful spiritual stupefying stupendous terrible tragic undefinable unexampled unforgivable unmentionable unnameable unparalleled unpardonable unprecedented untellable untouchable unutterable unwhisperable unworthy venerable vicious vile villainous wicked wonderful wrong