What does 甚だしい mean?
甚だしい is a Japanese adjective meaning “extreme, excessive, terrible” in English. It is written as 甚だしい in kanji, はなはだしい in hiragana, and hanahadashii in romaji. This word is part of JLPT N2 vocabulary.
Example sentence
あんなことを彼女に言うなんて非常識も甚だしい。
It's quite absurd of you to tell her that sort of thing.