An item or fabric that's breathable can move air easily and let moisture escape. This means that when you wear something made from a breathable material, you won't get too hot and sweaty.
Breathable comes up often when talking about clothes or shoes. Imagine you're on a hike in the summer and your shirt doesn't feel like it's suffocating you – probably because it's made of breathable fabric. Some sports brands use breathable materials for their running shoes, so that your feet don't get too wet from sweating. Even some bedding is labeled as breathable, to help keep you cool while you sleep.
(of air) suitable for breathing
