It means that a person can ask a doctor to kill themselves. To do that they must be suffering an illness and have decision making capability. 99.9% of the people who are suffering an illness don't have decision making capability.
Voluntaryism is the belief that all interaction should be voluntary and, by necessity, free of external coercion. It is heavily related to te NAP due to it's rejection of initiating force against others while still allowing for defensive actions.
Another key aspect to voluntaryism is self ownership: each individual owns him/herself and is therefore responsible for their own actions. Furthermore, no person or group has any legitimate claim to excersizing control over, or otherwise placing restraints on, the actions of others so long as the person's actions do not violate the equal rights of others.
Being a believer in voluntaryism, I am against the war on drugs, the death penalty, and all other government action because they all violate equal rights and force various involuntary interactions on individuals and groups.
When you have to leave a shit (I know, it's supposed to be take a shit, but in the immortal words of the late great comedian George Carlin, you don't take a shit, you leave a shit!), you tell whomever is nearby that you need to go and experience voluntary loss of stool.
This is the most gentle, curse-free way to say that you need to go and pinch a loaf.
{Paul}: Hold on a few minutes there George, I need to run and have voluntary loss of stool!
{George}: Ok, whatever Paul. :-/