A smelly tong is a tong that has been through a series of crappy events. This is often screamed out of the window as a profanity, or One would call themselves a smelly tong when handling their own poo!
A smelly tong is someone's dirty digits. Typically a "smelly tong" would consist of your thumb and index finger, both which have been shoved inside of your crack so that you can savor your flavor.
Ex: Smelly TONG!
Ex: Smelly Tong, you've done wrong.