When someone schlumps, they walk or sit in a lazy or slouching way.
Schlumping can be seen as lazy or not caring.
Examples:
He schlumps on the couch all day.
She schlumps into the room and plops down in the chair.
The tired dog schlumps over to its bed.
The cat schlumps lazily across the floor.
He schlumps around the house like a sleepy bear.
She schlumps into the room and flops onto the bed.