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???"