sealed-bid
adjective [ before noun ] uk/ˌsiːldˈbɪd/ us/ˌsiːldˈbɪd/
（买方竞投时出价保密的）秘密竞投
in which the amount offered by each person to buy something is not known by any of the other people involved
a sealed-bid auction/sale 秘密竞投的拍卖／销售
The sale of the land will be a sealed-bid process. 这块土地的出售将通过秘密竞投方式进行。