To defrost means to thaw something frozen, bringing it from a solid, icy state back to its normal temperature. When you take frozen chicken out of the freezer and let it warm up before cooking, you're defrosting it. Your refrigerator's freezer might need defrosting when ice builds up on the walls, requiring you to turn it off and let the ice melt away.

Defrosting reverses the freezing process. A car's defroster blows warm air on the windshield to melt ice and fog so the driver can see clearly. Some microwaves have a defrost setting that gently warms frozen food without cooking it.

In colder climates, people defrost their car windows on winter mornings, either by scraping off the ice or running the heater. It's a small but necessary task before heading out, turning a frosted, opaque window back into clear glass you can see through.