Everyone is wrong. A Dirty Sanchez is a slang term for filthy Mexican. Usually this term refers to a male particularly ones named Sanchez, Juan or Pedro. Usually the source or filth is low paying yard work but may also include dirt accumulated at home or in a vehicle due to cramped living conditions in Hispanic households.
A dirty Sanchez is when you are having anal and in the middle of sex she or he shits on your dick ,and u have to have pull out game and give them a mustache with the shit