He's the one who hasn't made any major mistakes yet, either.

Now it seemed as if that was going to be a major mistake.

A major mistake, then, is to show off, give them the feeling that you know more about a given subject than they do.

Something in his eyes suggested she'd just made a major mistake, though she wasn't exactly sure what it was.

But that was his first major mistake and he has been running hard for more than a year.

However, the country had changed, and that was a major mistake on their part.

They also have an opportunity to make a major mistake.

I may have been making major mistakes on the job.

This was the first major mistake of the battle for South.

I made a major mistake in the middle of the course.