Boiling
Seething
noun, する verb
The inflation of boiling water means that bubbles are being inflated in there and bubbling to the top. This is called boiling, or if it's happening in a person it's called seething.
ふっとう
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
スープが沸騰してグツグツいってますよ。
The soup was boiling and simmering.