Definition
to officially register your arrival by signing in when you reach a hotel, etc.
注册入住（酒店）
We booked in as soon as we arrived at the hotel.
我们一到达酒店就办理了入住手续。
I booked you in before you arrived.
我在你到达之前就帮你办理了入住。
They successfully booked into the hotel in Taipei.
他们成功地在台北的酒店办理了入住。