free transfer
noun [ C ] uk/ˌfriː ˈtræns.fɜːr/ us/ˌfriː ˈtræns.fɝː/
（无需支付足球选手前俱乐部费用的）自由转会
the act of moving a football player from one team to another without paying a transfer fee (= money that one club pays when buying a player from another club)
United risk losing him on a free transfer when his contract expires in May. 当他的合同在五月份到期时，联队有可能会因自由转会失去这名球员。