drop a clanger

drop a clanger (third-person singular simple present drops a clanger, present participle dropping a clanger, simple past and past participle dropped a clanger)

1. (informal) To commit a conspicuous and embarrassing blunder or gaffe, for example by saying the wrong thing at the wrong time.

   I dropped a clanger when I mentioned how well Mary's mother had been looking recently. I didn't know that she died two days ago.