1To reserve or charter something for exclusive use (to book so it's used only by a person or group).
社員旅行のためにバスを貸し切った。
We chartered a bus for the company trip.
結婚式の二次会でレストランを貸し切る予定だ。
We plan to reserve the restaurant exclusively for the wedding after-party.
映画館を貸し切って、友だちと上映会を開いた。
We reserved the movie theater for ourselves and held a private screening with friends.
2To lend something out completely; to let an item or space be used exclusively by someone else so that others cannot use it.
毎週その会議室はある会社に貸し切られていて、一般の予約はできない。
That meeting room is rented out to a company every week, so the public can't book it.
倉庫が長期にわたって個人に貸し切られ、地域の利用は制限されている。
The warehouse has been rented out long-term to an individual, restricting local use.