adj. 25B6; adjective
a frightful accident : HORRIBLE, horrific, ghastly, horrendous, serious, awful, dreadful, terrible, nasty, grim, dire, unspeakable; alarming, shocking, terrifying, harrowing, appalling, fearful; hideous, gruesome, grisly; informal horrid; formal grievous.
(informal) a frightful racket : AWFUL, very bad, terrible, dreadful, appalling, ghastly, abominable; unpleasant, disagreeable, lamentable, deplorable, insufferable, unbearable; informal God-awful; Brit. informal beastly.