grainy
Rough and bumpy with lots of tiny specks or dots.
When something is grainy, it has a rough, bumpy texture made up of tiny particles or grains, like beach sand or raw sugar. Run your fingers across a piece of sandpaper and you'll feel that grainy surface, made up of countless small, hard particles.
Those individual grains create that characteristic bumpy feeling when you run your hand through a bucket of rice or a bag of coffee beans.
Pictures and videos can be grainy too. When you zoom in on a photograph and it starts looking fuzzy and speckled instead of smooth, that's a grainy image. Old film cameras sometimes produced grainy photos, especially in low light, where the individual particles of film became visible. Digital cameras can create grainy images too when they struggle to capture enough light, making the photo look spotted or rough rather than clear and crisp.
Wood has visible grain as well, the lines and patterns you see running through a wooden table or floor. When woodworkers talk about working with or against the grain, they mean following or fighting those natural lines in the wood, although this use is related to grain rather than grainy itself.