pomyłka nietakt in English:

As a result of his carelessness, he made a serious blunder.

I am not responsible to you for my blunder.

What was she doing when she made that blunder?

I've made a blunder when I have visited my girlfriend's parents for the first time.

I accidentally called my girlfriend "mom". What a big blunder!

She's guilty of a grave blunder.

A-ha-ha-ha! What a blunder!

... could have turned my blunder into a huge piece...

1. I blundered badly by calling my wife by my ex-girlfriend's name. 2. A woman died as a result of a doctor's blunder.

she stopped, finally aware of the terrible blunder she had made

I've made an embarrassing blunder.

to make a terrible blunder, a series of political blunders

A last-minute blunder cost them the match.

He blundered around, looking for the light switch

He pleaded for me when I made a blunder.