na-adjective, noun which may take the genitive case particle 'no', noun
unbounded energy; matchless vigor; endless sexual stamina
A yojijukugo describing someone with extraordinary energy, often with a strong sexual connotation. Used as a noun or adjectivally with な or の.
He has boundless energy and works from morning till night every day.
精力絶倫な男として有名だ。
He is famous as a man of inexhaustible vigor.
A yojijukugo composed of 精力 (energy, vigor) and 絶倫 (peerless, unmatched). The exact historical origin is uncertain, but it follows a common four-character compound pattern.