A coyote sandwich is a used, rolled and tied sanitary napkin thrown into a public restroom trashcan. It is often eaten by wild animals that get into the trash cans or by desperate homelesspeople starved for protein.
My friendPete used to work for the forestry service and he had to clean coyote sandwiches out of the trash.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).