frightfully

adverb

fright·​ful·​ly -f(ə)lē 

-li

: in a frightful manner: such as

a

: alarmingly

worried by the frightfully fast movement of the car over the dark road

b

: egregiously, shockingly

the frightfully cruel treatment of the animal

c

: very, extremely

I'm frightfully sorry I inconvenienced you

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