lively; vigorous; energetic; healthy; avid (e.g. desire); rich (e.g. imagination)
full of (energy, appetite, curiosity, etc.); brimming with
若者は好奇心が旺盛で何でも学びたがる。
Young people are full of curiosity and eager to learn everything.
旺盛な食欲に驚かされた。
I was amazed by their hearty appetite.
彼は創作意欲が旺盛な作家だ。
He is a writer with a strong creative drive.