walk-in

n.

person who walks in without having an appointment

"the emergency room was overrun with walk-ins"

an operative who initiates his own defection (usually to a hostile country) for political asylum

an assured victory (especially in an election)

同义词：waltz

a small room large enough to admit entrance

1. The doctor accepts walk-in patients every Wednesday afternoon.
   这位医生每周三下午接受不预约的患者。
2. The restaurant has a walk-in policy, so you can come anytime without a reservation.
   这家餐厅有不预约的政策，所以你可以随时来，不需要预定。