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"
awful,
dire,
direful,
dread,
dreaded,
dreadful,
fearful,
fearsome,
frightening,
horrendous,
horrific,
terrible