first class seat (JR train); Green Car seat
Refers specifically to a seat in the first-class 'Green Car' compartment on JR trains. The term is used in the context of JR's Green Car service.
See also: JR · グリーン車 (グリーンしゃ)
I reserved a first-class seat on the Shinkansen.
Green Car seats are more spacious and comfortable than regular seats.
Compound of グリーン (from English 'green', referring to the Green Car service) and 席 (seat).