The act in which one consumes food whilst taking a dump, often because the individual is in a hurry and does not have the time to do both one at a time. Not to be confused with excrete.
"Shit I don't have time to eat this and take a dump! I need to get to class and take that exam. Guess it's time to excreat."
A person who doesn't flush the toilet after a bowel movement in hopes that someone else will stumble upon and be able to admire their work of art. Some hard-core excrebitionists have been known to go so far as to refrain from wiping in order to avoid obstructing the view.
Either Shaina is very forgetful of flushing the toilet, or she is just a big-time excrebitionist.