taru-adjective, adverb taking the 'to' particle
full of vitality; vivacious; energetic
Describes a lively, energetic state or manner, often used in literary or formal contexts. Functions as a taru-adjective or adverb with と.
彼女の生気溌剌とした笑顔が印象的だった。
Her vivacious smile was impressive.
子供たちは生気溌剌と遊び回っている。
The children are playing around full of energy.
A four-character compound combining 生気 (vitality, life force) and 溌剌 (lively, vigorous). The exact historical derivation is uncertain, but it is used as a set phrase in literary Japanese.