The phrase
"formula poop" refers to the bowel movements or stools of a baby who is being fed formula milk rather than breast milk.
Full definition
Breastfeeding poop will be either mustard yellow, green or brown,
while formula poop will be a yellowish - brown or brown.
The smell is probably due to the formula; studies have shown that
formula poop is a lot more smelly than breast milk poop.
Breast milk poop smells a hell of a lot better than
formula poop.
Breast milk is absorbed into the body quickly and doesn't take very long to be processed, so breast milk poo comes out quickly, and it's more often yellow or lighter in color than
formula poop.
This may be to much information but one thing that really surprised me is
her formula poop looked more formed, dark brown / green and smelled like an adult poop.
Typically,
formula poop has a stronger smell.