Bad words

I learned Spanish in Honduras, I had taken Spanish 101 in university but that only gets you basically nowhere. In learning Spanish my mother-in-law and husband were very guarded about the words I learned, trying as hard as they could that I learned as little bad words as possible. With the help of esposo's aunt it did not work out too well, but still they both tried as hard as they could.
One day working at the store my mother-in-law was very upset at an employee. She was going on and on about how the display was in the wrong place, but she kept on saying this word over and over, and I had no clue what it meant. Being the curious person I went to esposo and asked him. I said "esposo, what does mierda mean?" his faced dropped, he was upset "who told you that word?" me, looking confused, "your mom" pointing to the part of the store where she was at. Looking slightly defeated esposo replied "shit."