Definition of booster seat in English English dictionary
a seat to help raise a child in a vehicle so that the vehicle's seat belt fits properly
special seat designed to be placed on top of an adult chair in order to raise a small child to the level of a table; minimal car seat designed for a small child (used with an adult safety belt)
A booster seat or a booster cushion is a special seat which allows a small child to sit in a higher position, for example at a table or in a car. 'booster .chair 'booster .cushion a special seat for a small child that lets them sit in a higher position in a car or at a table