If someone looks or feels dreadful, they look or feel very ill, tired, or upset. Are you all right? You look dreadful
If you say that something is dreadful, you mean that it is very bad or unpleasant, or very poor in quality. They told us the dreadful news = awful, appalling + dreadfully dread·fully You behaved dreadfully
emphasis Dreadful is used to emphasize the degree or extent of something bad. We've made a dreadful mistake = terrible + dreadfully dread·fully He looks dreadfully ill
causing fear or dread or terror; "the awful war"; "an awful risk"; "dire news"; "a career or vengeance so direful that London was shocked"; "the dread presence of the headmaster"; "polio is no longer the dreaded disease it once was"; "a dreadful storm"; "a fearful howling"; "horrendous explosions shook the city"; "a terrible curse"
{s} terrible, horrible, inspiring fear and dread; inspiring awe and great respect, awful
exceptionally bad or displeasing; "atrocious taste"; "abominable workmanship"; "an awful voice"; "dreadful manners"; "a painful performance"; "terrible handwriting"; "an unspeakable odor came sweeping into the room"