seater
n. countable B1 Intermediate US //ˈsitɝ// seater
n. a word used with a number to say how many people can sit in a car, on a sofa, or at a table. For example, a four-seater car has four seats.
n. A suffix-derived noun used in combination with a numeral to specify the seating capacity of a vehicle or piece of furniture.
We bought a comfortable three-seater sofa for the living room.
Since they have four children, they had to trade their small car for a seven-seater van.
The airline operates a fleet of fifty-seater regional jets to connect smaller provincial hubs with the capital city.
Usage
Almost always preceded by a number or a numerical adjective (e.g., 'two-seater', 'multi-seater') to form a compound noun.