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"
Frightening.
"The dark storm clouds overhead made a fearful sight for everyone watching."
Extremely; fearfully.
"The team was fearful of missing their deadline, so they worked through the night without a single break."