Definition: An animal that has been run over and killed by a car; any disgusting substance that is on the ground.
Example:
1) Maura's pet turtle escaped last week and I'm afraid it's probably street pizza by now.
2) That poor little dog -- now he's just street pizza.
Etymology: 'Pizza' is a popular food that is flat and has lots of red tomato sauce, and 'street' means road or highway. This phrase is a comical reference to unpleasant organic materials that are found on roads and sidewalks.
Synonyms: road kill