vigorously; with energy; assertively
Describes doing something with lively energy, confidence, or forcefulness; often used for speaking, acting, or moving in a spirited manner.
He replied vigorously.
The players energetically ran out onto the field.
Standard kanji spelling; よく is usually written in kana.
Alternate spelling using the kanji 良 for よく; less common.
Compound of 威勢 (いせい, 'spirit, energy') and the adverbial form よく of the adjective よい ('good').