What is a mealy tomato, and how would one use one? When people say a tomato is or isn't mealy, what does that really mean? I've never had a tomato that was grainy, as it's sometimes described. Is that even possible? That sounds like a tomato with sand in it. How would you personally describe the consistency without using the dictionary definition?

Also, what are mealy tomatoes good for?
Yup, tomatoes can most definitely be a bit grainy. It's not a hard graininess like sand, but a softer graininess. The best comparisons that come to mind are hydrated but uncooked cornmeal or slightly wet breadcrumbs. Instead of being juicy and smooth (whether firm or soft), you'll notice a bit of small texture. It'll probably also be less juicy, and the flavor may not be as fresh and full as you'd like. If you've never had one, awesome - you've had good tomatoes!

It's also a common texture in some varieties of apples, especially when not too fresh. It's especially noticeable there; instead of a crisp crunch as you bite through it'll feel a little crumbly.

They'd be all right for things where you're going to cook them thoroughly so you won't notice the texture, like spaghetti sauce, though again the flavor may suffer as well. For anything remotely fresh, they're still edible, just noticeably not as good.