1 : a soft object or part that is used to make something (such as a seat) more comfortable or to protect a surface from damage : a soft pillow, pad, etc.
a seat/sofa cushion
There is a cushion under the rug to protect the floor.
a cushion of air (=a layer of air that provides support or protection to something)
2 : any one of the rubber parts that the ball bounces off along the inner edges of a billiard table
3 : something (such as an extra amount of money) that you can use to reduce the bad effect of something (such as an unexpected problem or expense)
We didn’t have a financial cushion when my husband lost his job.
— often + against
We use our savings as a cushion against major expenses.
4 : a lead in a game or competition that is large enough to allow the leader to feel confident about winning — usually singular
The team enjoyed a 6–0 cushion in the last inning.