If something is cancellable, it can be stopped or not used if you decide you no longer want it.

Under certain conditions the contract to buy will be cancellable. 在某些情况下，购买合同可以取消。

If there is any uncertainty around your plans it might be better to book a cancellable hotel. 如果您的计划有任何不确定性，最好预订可取消的酒店。