noun
Used in professional sports contexts for a player who is not under contract with any team and is free to negotiate with any club.
彼は今シーズン、自由契約選手としてどの球団とも交渉できる。
This season, as a free agent, he can negotiate with any team.
Compound of 自由 (free) + 契約 (contract) + 選手 (player). A straightforward calque from English 'free agent'.