1 bad, serious, grave, severe, acute, distressing, disagreeable, nasty, foul, unbearable, dreadful, loathsome, hideous, vile, intolerable, awful, Colloq rotten, lousy, beastly:
I've had a terrible virus.
2 bad, remorseful, regretful, rueful, sorry, contrite, ashamed, conscience-stricken, guilty, distressed, dreadful, awful, Colloq rotten, lousy, beastly:
I felt terrible having to tell the neighbours about their cat.
3 unhappy, unpleasant, disagreeable, awful, miserable, joyless, wretched, unfortunate, Colloq rotten, lousy, beastly:
We spent an absolutely terrible evening at the theatre.
4 gruesome, grisly, macabre, gory, grotesque, brutal, savage, horrible, horrendous, terrifying, terrific, harrowing, horrid, horrifying, ghastly, frightening, frightful, unspeakable, monstrous, dread, terrible, appalling, shocking, alarming, awful, foul:
The casualties that were arriving had the most terrible wounds.
5 disgusting, revolting, nauseating, nauseous, offensive, vomit-provoking, obnoxious, stomach-turning, stomach-churning, abominable, mephitic, noisome, noxious, loathsome, horrible, hideous, terrific, awful, evil, vile, rotten, awful:
The compost heap was giving off the most terrible stench.
6 terrifying, frightening, frightful, fearsome, formidable, redoubtable, awesome, awe-inspiring, terrific:
The animal gave a terrible roar and charged into the clearing.