full of vitality; exuberant; effervescent
Describes a state of overflowing energy and high spirits; somewhat literary or emphatic.
He is a young man brimming with vitality.
The audience was moved by the exuberant speech.
元気 is a common, everyday word for being well or energetic; 気力横溢 is a more literary, emphatic expression for overflowing vitality.
活力 refers to vitality or energy as a quality; 気力横溢 emphasizes the state of being full to the point of overflowing.
Compound of 気力 (vitality, energy) and 横溢 (overflowing, brimming). The exact historical derivation is uncertain, but the word is formed from standard Sino-Japanese elements.