Definition of frightful :
1. Full of fright; affrighted; frightened.
2. Full of that which causes fright; exciting alarm; impressing terror; shocking; as, a frightful chasm, or tempest; a frightful appearance.
demoralizing, ominous, lurid, cowardly, macabre, vile, extraordinary, august, howling, fearsome, slimy, unspeakable, ugly, majestic, awed, monstrous, trepid, grievous, harrowing, wondrous, marvellous, horrendous, timorous, horrific, bad, fearful, spooky, atrocious, charming, disturbing, offensive, disquieting, awing, weird, direful, good, stately, amazing, formidable, surly, dreaded, wicked, solemn, hair-raising, gruesome, calamitous, painful, scary, flagitious, despicable, dread, repellent, shocking, frightening, severe, worthless, terrific, uncanny, nasty, awe-inspiring, grand, enormous, fear, rattling, inconceivable, portentous, redoubtable, imposing, wretched, tremendous, marvelous, fantastic, bloodcurdling, horrifying, noble, abominable, eerie, unworthy, awesome, wonderful, grisly
awful (part of speech: adjective)
- But the last part of my journey was frightful. - "The Reclaimers", Margaret Hill McCarter.
- It- it's such a frightful responsibility." - "The Keeper of the Door", Ethel M. Dell.
- After this exploit the huntsmen, anxious to discover the child whose cries resounded in this frightful habitation, eagerly descended into it. - "Eastern Tales by Many Story Tellers", Various.