When you blurt something out, you haven't thought about it first, and you haven't planned what you're going to say. Your emotions are running high. You might feel deeply sad or deeply happy, or very scared or very surprised, or just mad, shocked, annoyed, or excited. No matter what the feeling is, it's a strong one—and strong feelings often stop us from slowing down to think, "Should I say this? Is it a good idea to say this? Is it true? Is it kind? Is it necessary?"
So, often, when we blurt something out, it's unkind, or it's too much information and we shouldn't be sharing it.
The word "blurt" is probably echoic, or onomatopoetic, like "oof," "splat," "gargle," and "flip-flop." That means someone probably invented this word by copying the sound of people spitting out words. Can you hear it? Blurt!