A slab is a thick, flat piece of something solid, usually something heavy like stone, concrete, or metal. When builders pour concrete for a garage floor or patio, they create a concrete slab: a broad, level surface that might be four to six inches thick. Ancient peoples like the Egyptians moved massive stone slabs weighing many tons to build monuments.

In cooking, a slab of ribs means a whole section of connected ribs before they're cut apart, while a slab of bacon is the whole unsliced chunk before it becomes individual strips. You might see a butcher's counter displaying a huge slab of cheese or a bakery showing off a beautiful slab cake baked in a flat rectangular pan.

The word suggests something substantial and weighty. A thin sheet of paper isn't a slab, but a thick piece of marble countertop is. When geologists study rock formations, they might examine slabs of ancient stone that reveal layers of Earth's history. The word captures both the flatness and the impressive solidity of these thick pieces.