旅客 (lǚ kè) means 'traveler' or 'passenger' — it refers to someone on a journey, especially using public transport (airports, trains). It is more general than 乘客 (chéng kè), which specifically means a passenger on a vehicle, and different from 游客 (yóu kè), which means a tourist (someone traveling for sightseeing). Use 旅客 for travelers in transit contexts.