Longman Dictionary of Contemporary English
car seat
noun
EXAMPLES FROM CORPUS
▪ Ensure you use the correct fitting kit for your make and model of car seat.
▪ He thought about hiding it in the car seat, but Firebug was always moving the thing around.
▪ Miguel stood there by the car seat, thinking about Amelia.
▪ Miguel told him, picking a spot opposite the car seat for the desk.
▪ Officers found used hypodermic needles in a trailer in the backyard next to an infant car seat.
Wiktionary
car seat
n. 1 A seat in a motor car. 2 A detachable motor car seat equipped with a harness to secure a young child.
WordNet
car seat
n. a seat in a car
Wikipedia
Car seat
A car seat is the seat used in automobiles. Most car seats are made from inexpensive but durable material in order to withstand prolonged use. The most common material is polyester.