sleeping car

carriage in a train that is equipped with special couches for sleeping

The sleeping car or sleeper is a railroad passenger car that can accommodate all its passengers in beds of one kind or another, primarily for the purpose of making nighttime travel more restful. The first such cars saw sporadic use on American railroads in the 1830s and could be configured for coach seating during the day. Some of the more luxurious types have private rooms, that is to say fully- and solidly-enclosed rooms that are not shared with strangers.
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Noun
1. a passenger car that has berths for sleeping
(synonym) sleeper, wagon-lit
(hypernym) passenger car, coach, carriage
(part-meronym) drawing room