Smutching means making something dirty with marks or stains.
Smutching can make things look messy or not nice.
Examples:
I accidentally smutched my shirt with paint.
She smutched her face with chocolate.
The dog smutched the carpet with mud.
He smutched his pants with grease.
The kids smutched the walls with crayons.
Stop smutching the floor with your dirty shoes!