Anything that makes you feel horrified is frightful, whether it's a frightful traffic accident on the highway or your brother's frightful new haircut.
This adjective is more common among British English speakers than American ones, but no matter where you live it's a good way to describe something that causes distress, shock, or offense. You may look frightful after falling in the swimming pool while fully clothed, but the frightful sounds coming from a haunted house might cause you to feel more actual terror — or fright.