A baby buckled into his car seat.
car seat definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a seat in an automobile; specif., a portable seat that fastens onto a car's built-in seat and is used for securing a small child
car seat definition by American Heritage Dictionary
A small removable seat that is equipped with a restraining device or harness and can be fastened to the seat of a vehicle for securing young children.