na-adjective
Describes something powerfully energetic, wild, or aggressive. Often used with nouns like 勢い, 暑さ, or 動物.
今年の夏は猛暑だった。
This summer was intensely hot.
その犬は猛スピードで走った。
The dog ran at a ferocious speed.
prefix
Prefix used in compounds to indicate an extreme degree. Common in words like 猛暑, 猛吹雪, 猛勉強.
猛吹雪で視界がまったくきかなかった。
In the severe blizzard, visibility was completely lost.