That which, after a certain amount of time spent
exploring one's
stomach lining, decides not to stay and
exits violently out the front door.
Also the verb describing the ejection of said stomach contents.
See also: vomit, spew, hork, puke, hurl, ralph, blow chunks, retch, purge, in'n'out, Lose Weight Fast!, lose yer lunch, and "that Chinese food was how old???"