If something is water-repellent, water does not soak into it. The water sits on the surface in little round drops and rolls off, so the thing under it stays dry — or mostly dry. This is usually not a natural property of the material; a coating or spray has been put on it. We say it about coats, jackets, shoes, backpacks, tents, phone cases, and sometimes about paint or wood treatment.

The important thing is that water-repellent is NOT the same as waterproof, and shops use the difference carefully. Waterproof means water cannot get through at all — you can stand in heavy rain and stay dry. Water-repellent means water is pushed away, but if the rain is hard enough, or long enough, or if you sit down in a puddle, water will eventually get in. So water-repellent is the weaker promise. Think of it as 'good for a short walk in light rain', not 'good for a typhoon'.

There is also a slow, quiet problem that catches people out: the coating wears off. A jacket that repelled water beautifully when it was new can stop doing it after a year of washing and rubbing. The jacket has not broken; the surface treatment has just worn away, and you can buy sprays to put it back. Shops often write 'water-repellent' as one word pair with a hyphen before a noun (a water-repellent jacket), and it is a fairly technical, product-label kind of word — you see it printed on a tag much more often than you hear a friend say it. In everyday speech most people just say 'it doesn't get wet' or 'rain rolls off it'.