Okay, so imagine you have a tomato. You can hold it in your hand and it's all round and smooth. Now, imagine you take that tomato and squeeze it really hard. What happens? The tomato squishes and all the insides come out. That's what we call a "splatty tomato".
Sometimes, people use the term "splatty tomato" to describe something that's messy or chaotic. For example, if you were playing a game of tag with your friends and everyone was running around and bumping into each other, someone might say, "This game is like a splatty tomato!"
But overall, a splatty tomato is just a tomato that's been squished and made into a mess.