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"
Something that is horrendous is very unpleasant or shocking. He described it as the most horrendous experience of his life = horrific
Some people use horrendous to describe something that is so big or great that they find it extremely unpleasant. the usually horrendous traffic jams. = dreadful + horrendously hor·ren·dous·ly Many outings can now be horrendously expensive for parents with a young family