Vomiting is the forceful expulsion of the contents of one's stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

 through the mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 and sometimes the nose
Human nose
The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...

. Vomiting can occur due to a wide variety of conditions; it may present as a specific response to ailments like gastritis
Gastritis is an inflammation of the lining of the stomach, and has many possible causes. The main acute causes are excessive alcohol consumption or prolonged use of nonsteroidal anti-inflammatory drugs such as aspirin or ibuprofen. Sometimes gastritis develops after major surgery, traumatic...

 or poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ing, or as a non-specific sequela
A sequela) is a pathological condition resulting from a disease, injury, or other trauma.Chronic kidney disease, for example, is sometimes a sequela of diabetes, and neck pain is a common sequela of whiplash or other trauma to the cervical vertebrae. Post-traumatic stress disorder may be a...

 of disorders ranging from brain tumor
Brain tumor
A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...

s and elevated intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...

 to overexposure to ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

. The feeling that one is about to vomit is called nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, which usually precedes, but does not always lead to, vomiting.

You know in some cultures, they only eat vomit. I never been there before, but I read about it... IN A BOOK! :— Ben Stiller in Dodgeball: A True Underdog Story