Someone who demonstrates extraordinary skill and knowledge about anything related to poop.
That turd savant could smell your shit blindfolded and tell you what you ate for breakfast!
A turd savant is the Rainman of poop. This unique genius can tell you the state of your health with a quick look at your poop.
Turd savant: See how that log veers to the left? Not good. Drink chamomile tea at bedtime for a week to get more rest. Then snap a pic of your morning poop, text it to me and I will give you an update.