The two characters combine in a very direct and literal way: 无 (without) + 座 (seat) = 无座 (without a seat).
The term `无座` is deeply intertwined with 春运 (Chūnyùn), the Spring Festival travel rush. This 40-day period surrounding the Chinese New Year is the largest annual human migration on Earth, with hundreds of millions of people—students, and especially migrant workers—traveling from cities back to their rural hometowns to be with family. During this time, the demand for train tickets is astronomically high, and they sell out in seconds. The `无座` ticket is a pragmatic solution by the railway system to maximize capacity and allow as many people as possible to make this essential journey.