booster seat 
(also booster cushion)
noun
An extra seat or cushion placed on an existing seat for a small child to sit on.A booster seat helps the seat belt fit better for older children who are not big enough for the safety belt alone....
- Many parents incorrectly believe that their child is too old for a child seat or a booster seat.
- A belt-positioning booster seat will help position the seat belts on your child's body and will fit your child until she weights about 60-80 pounds.
- McBurney's point
- MCC
- McCain, John
- McCarthyism
- McCarthyite
- McCarthy, Joseph
- McCarthy, Mary
- McCartney, Linda
- McCartney, Sir Paul
- McClellan, George Brinton
- McClintock, Barbara
- McConkey
- McConochie
- McCormack, John
- McCormick, Cyrus Hall
- McCourt, Frank
- McCoy
- McCullers, Carson
- McCullough, Colleen
- McCune–Albright's syndrome
- McCune–Albright syndrome
- McDonaldisation
- McDonaldise
- McDonaldization
- McDonaldize