1)A disease by which a human suffers by being constipated/having diaria and also suffering from increased amount of vomiting at the same moment. vomshitting may occur when a person is shitting in toilet whilst shitting he may over push his shit in his intestines which may lead to force pushing on the stomach which will cause the person to vomit and shit at the same time.
To avoid vomshitting one must not over push his shit instead relax and let your anus do its buisness.
Another advice woulf be decresing the amount of drinking alcohol and decreasing masturbating.

2) The word is said in a situation where someone is shocked and grossed out from the person he's speaking to. So the person will reply by saying "Are vomshitting me?" becasue that person had an erge to vomit due to the disgusting and shocking thing that was told to him.

When you eat dirt for the first time and leave your family to build a shack in the woods