The Oxford Thesaurus An A-Z Dictionary of Synonyms - dreadfuladj.

1) bad, awful, terrible, Colloq rotten, Slang lousy: That TV soap opera is simply dreadful. 2) grievous, dire, horrible, horrendous, horrifying, horrid, monstrous, fearful, feared, frightful, dread, frightening, shocking, alarming, appalling, fearsome, hideous, ghastly, atrocious, heinous, wicked, evil, iniquitous, villainous, flagitious, fiendish, diabolical, devilish, demonic, malevolent, maleficent, malefic, Colloq scary: They did the most dreadful things to political prisoners.