A brick is a rectangular block made from baked clay or other materials, used for building walls, houses, roads, and other structures. If you've ever seen a red or brown building with a pattern of small rectangles, you were looking at bricks stacked together with cement or mortar between them.

Bricks have been used in construction for thousands of years because they're strong, durable, and fire-resistant. The ancient Romans built roads and buildings with bricks that are still standing today. Modern construction workers still use bricks to build houses, schools, and fireplaces, though today's bricks come in many colors and materials beyond traditional clay.

When people call something “solid as a brick” or a “brick wall,” they mean it's extremely strong and hard to break through. A brick of something can also mean a rectangular block: you might see a brick of cheese at the grocery store or a brick of gold in a museum.

In sports, when someone throws up a shot that clangs badly off the rim, people sometimes call it a brick because it hits with a heavy thud. And if something electronic stops working completely, you might hear someone say it's been “bricked,” meaning it's now as useful as a brick, just sitting there doing nothing.