1.
fury; ferocity; devastating force
Overwhelming, destructive power, especially of natural disasters, epidemics, or other forces beyond human control. Almost always used with を振るう (to rage, to wreak havoc).
Usage
Almost exclusively used in the fixed phrase 猛威を振るう (to rage, to wreak havoc). Rarely appears outside this collocation. Subjects are typically natural disasters (台風, 地震), diseases (インフルエンザ, ウイルス), or other destructive forces.
This word is a bound noun — it almost never appears alone without を振るう. Learning the full phrase is more useful than learning the word in isolation.