1. Someone who believes and promotes the ending of a pregnancy: The speaker was a well-known abortionist who advocated supporting the legal termination of pregnancies.
2. An individual who makes a business of ending a pregnancy illegally: The backstreet abortionist has recently been arrested by the police.
3. People who support, or advocate ending pregnancies when a woman wants it to be done: The noisy crowd in front of the clinic included many well-known abortionists.
4. Anyone who takes the action of stopping a project, a mission, etc, before it is completed: The engineer for the city was an abortionist who advocated discontinuing the building of the expensive bridge because of the excessive costs.