If someone is shlumpy, they look messy or untidy, like they don't care about their appearance.
Shlumpy can make people think of being tired, not feeling well, or not caring about how they look.
Examples:
She looks shlumpy in her old clothes.
He felt shlumpy after a long day at work.
The shlumpy man didn't comb his hair.
I feel shlumpy when I don't get enough sleep.
The shlumpy cat didn't clean its fur for days.
The shlumpy dog looked like it had a long day.