If something is smearier, it has more dirt or mess on it.
Smearier things are usually not good. People don't like things that are smearier.
Examples:
The old shirt is smearier than the new one.
The kitchen floor is getting smearier and smearier.
The dog made the house even smearier.
I don't want to play in the smearier mud.
The smearier the window, the harder it is to see through.
The smearier the dishes, the longer it takes to clean them.