used to emphasize what you are saying, especially how bad something is:
The weather outside was frightful.
Of course the cleaning is a frightful bore.
(informal) used to emphasize how bad sth is 极坏的；很糟的 SYN awful, terrible
It was absolutely frightful!
简直糟透了！
This room’s in a frightful mess.
房间里乱七八糟。