noun
furious; infuriated; enraged
Literary and emphatic expression describing extreme anger, often with the image of hair standing on end. Used in formal or dramatic contexts.
彼の不正を知り、怒髪天を衝く思いだった。
Learning of his injustice, I felt my fury reach the heavens.
激怒 is a standard noun for 'rage' or 'fury', whereas 怒髪天 is a more vivid, idiomatic expression.
Derived from classical Chinese literature, literally meaning 'angry hair (reaches) heaven', describing rage so intense that one's hair stands on end.