The superlative form of 'schleppy', which means messy, untidy, or not put together well.
This word can make people think of someone who doesn't care much about how they look or how they keep their things.
Examples:
Her room is the schleppiest in the house.
He always wears the schleppiest clothes.
The schleppiest person in the office is always late.
That's the schleppiest sandwich I've ever seen!
The schleppiest dog in the park was covered in mud.
She always has the schleppiest backpack at school.