1. To expel the contents of the stomach through the mouth as a result of a series of involuntary spasms of the stomach muscles.
2. To eject part or all of the contents of the stomach through the mouth, usually in a series of involuntary spasmic movements.
3. To gush forth; to send something out in a forceful stream, or be ejected forcefully: "He was so angry that he could only vomit curses."
4. To be discharged forcefully and abundantly; to spew or to gush: "The water pipe burst and the water vomited forth."
5. Etymology: "act of expelling contents of the stomach through the mouth", from Latin vomitare, "to vomit often".

Vomit and vomitus are synonymous as nouns although only vomit is used as a verb. The act of vomiting is also called emesis. From the Indo-European root wem- (to vomit), the source of the words; such as, emetic and wamble, "to feel nauseated".