What is the defintion of poop?

It is the waste produced by our bodies. Your body cannot make use of everything you ingest so "poop" is the waste left over after digestion is finished. The poop is initially quite liquid but once the long intestine takes out the water you poop. This process will take to up to 1 day MAX days.

addendum It is otherwise known as feces, faeces, excrement, stools, No 2s, body waste, and so on. No doubt other languages also have many alternate names.

Constipation is usually caused by insufficient dietary fibre and inadequate water intake.