Like to say something bad,offensive,embarrassing,etc to somebody you didn't you mean to say
Yes, it can mean unintentionally, but it can also mean “suddenly” or “abruptly” without being completely unintentional. It’s not always really “bad, offensive, embarrassing” either.
For example, I wanted to tell my best friend Sharon her new haircut didn’t really suit her but I was waiting for the right time to raise the subject sensitively. In the end though, I just blurted it out when we were on the bus together, but we managed to have a good laugh about it when she told me I needed a haircut too.
I agree with Orbital Aussie — it’s more about the suddenness than anything else.
Here are some more examples:
- Melissa is in the bus with her co-worker Lena. She has been thinking about changing careers for a while. Lena is talking to her about work and how excited she is for the next assignment. Melissa gradually gets more frustrated. Finally, she opens her mouth to respond and blurts out “I’m gonna quit this job.” (Intentional, sudden. Not necessarily bad.)
- Daisuke is hanging out with his friends. Someone asks him a question about who he likes at work. At first, he doesn’t mean to answer, but in the end he blurts it out anyway. (Unintentional, sudden. This case is more embarrassing.)
- Adhiti and Luis are walking around all day to interview people for a film. After a long day of work, they’re tired. They notice a sign for a relaxing coffee shop nearby, look to each other, and blurt out “let’s get coffee!” (Intentional, sudden. Not embarrassing or bad at all.)
Basically, as long as it’s sudden and fast, you can use “blurt out.”
If the subject is talking slowly (as if giving a speech), they are probably not blurting it out.