Poop usually gets stuck halfway out because it is too hard, too dry, or too large for the anus to pass comfortably. This is most often linked to constipation.
When stool sits in the colon for too long, it loses water and becomes harder. A harder stool needs more force and a wider stretch to pass, which can cause it to get stuck partway.
This can feel uncomfortable or even painful. Some people also feel like they need to push, but pushing too hard can make the problem worse.