full of energy; highly motivated; full of drive
Describes a person or their state as being brimming with mental energy, motivation, or vitality. Often used in formal or written contexts.
He always tackles his work with great energy and motivation.
The highly motivated young people started a new project.
元気 is a more general, everyday word for being well, healthy, or lively, while 気力旺盛 specifically emphasizes abundant mental drive and motivation.
意欲的 means 'eager' or 'motivated' and focuses on willingness to do something, whereas 気力旺盛 describes a state of having plentiful energy and drive.
Compound of 気力 (mental energy, drive) and 旺盛 (vigorous, abundant). The exact historical derivation is uncertain, but the combination is transparently formed from these two Sino-Japanese elements.