When you take moisture out of the air, you dehumidify it. If there's mold growing in your damp basement, you might need to dehumidify things down there.
This verb describes a process of removing humidity, or dampness, from the air. If you want to dehumidify your house, you'll need a dehumidifier, a machine with the sole purpose of drying out the air in a room. Humidity isn't necessarily a bad thing, but excessive amounts of it can cause mildew and mold to grow and spread, especially when it's paired with high temperatures.