To have become thinner, especially by losing weight or by making something smaller.
When something is slimmed, it is usually seen as a good thing, making people feel happy or proud.
Examples:
She slimmed down by eating less junk food.
He slimmed his wallet by taking out old receipts.
The dress slimmed her figure.
The cat slimmed down after running around all day.
The elephant slimmed down so much, it could fit in a tiny car.
The room slimmed when they took out the big table.