put one`s foot in one`s mouth

elszólja magát, rossz helyen rossz dolgot mond
say something that is the wrong thing to say in a situation, to say something embarrassing or wrong, to say something that one will regret, to make an error 

  • John put his foot in his mouth when he asked the overweight girl if she was pregnant.
  • When I told Ann that her hair was more beautiful than I had ever seen it, I really put my foot in my mouth. It was a wig.
  • He really put his foot in his mouth when he told her about the surprise party.  
  • I really put my foot in my mouth during the interview.
A: This is a great party.
B: Yeah it is!
A: Whose house is this? It is so ugly.
B: It’s my house.
A: Oh. I just put my foot in my mouth.  

have a big mouth 
( talk too much, especially about things that should be secret)
  • She's got such a big mouth - the news'll be all over the village by tomorrow. I knew I shouldn't have mentioned the letter. Oh dear, me and my big mouth!