Corrugated means having a surface shaped into alternating ridges and grooves, like waves frozen in place. If you've ever looked closely at a cardboard box, you've seen corrugation: the cardboard has a wavy middle layer sandwiched between two flat sheets.

This wavy pattern serves a structural purpose: it makes materials much stronger without adding much weight. A flat piece of cardboard bends easily, but corrugated cardboard can support heavy books or dishes because those ridges work like tiny architectural arches. Engineers use the same principle with corrugated metal for roofing in warehouses and sheds: the waves make thin metal sheets strong enough to span long distances and bear heavy loads.

You'll find corrugation in unexpected places. Some roads have corrugated strips (called rumble strips) that make your car vibrate when you drift toward the shoulder. Corrugated pipes for drainage are more flexible and stronger than smooth ones. Even the sole of a hiking boot might have a corrugated pattern for better grip.

That's exactly what corrugation looks like: a series of neat, parallel ridges that turn a weak, flat surface into something surprisingly sturdy.