flared nostrils
Describes nostrils widened in anger or strong emotion. Rare term; more commonly expressed with phrases like 鼻の穴を膨らませる.
彼は怒り鼻で、今にも爆発しそうだった。
With flared nostrils, he looked ready to explode.
Compound of 怒り (anger) and 鼻 (nose). The exact historical derivation is uncertain, but the meaning is transparent from its components.