make a blooper
make a bloomer
make a blunder
make a boob BrE

The children might not realize, and make a social blunder.

But the most amazing thing is that computer made a blunder on the last move.

He made a major blunder in laying out the line, however.

You've made a silly blunder, and you may as well own up to it.

The slam of the door told him he had made a bad blunder.

Did anyone near him present the case that he might be making a great historic blunder?

In Mark the feeling grew of just having made an enormous blunder.

She had just made a huge blunder going independent at the Academy, but this was different.

And if so, why did an experienced politician make such a blunder?

I read it and thought that Google had made a huge blunder.