People who own buildings with apartments or rooms that are in very bad condition and charge people to live there.
Slumlords are usually seen as bad because they don't take care of the places where people live.
Examples:
The slumlords don't fix anything in the building.
The government is trying to stop slumlords from renting out their buildings.
The slumlords make a lot of money from the people who live in their buildings.
The slumlords are so cheap, they won't even fix the broken windows.
The slumlords are so mean, they don't care if the people living there are happy or not.
The slumlords are like the villains in a story, making people live in terrible places.