Noun; One who commits suicide by securing a plastic bag over his or her head and pumping in a gas, thereby dying of asphyxiation; the individual's head in the bag gives him or her passing resemblance to an astronaut.
Nico was so upset by Lou's rejection of her that she decided to end her life as a gastronaut.
A drinking game: On the show Acient Aliens, you drink every time the narrator says "ancient astronaut theorists". If the "ancient astronaut theorist" is from DeVry University, you drink twice.