someone who holds a negative value to human birth. usually for environmental reasons (overpopulation), or because life sucks and they don't want to put someone else through it
tim: do you ever wanna have children?
sarah: not of my own, i'm an antinatalist. i am open to adoption though!
A person that goes against or is opposed to the social and political order of the day. Someone against the establishment.
After he studied his state representative's beliefs he decided to become an antiestablishmentarianist. My folksaren't happy that I am an antiestablishmentarianist.