Vomit
The body forcibly rejecting what was taken in — an emergency expulsion of something the system could not accept.
Vomit in a dream is the dream's image of the body's forcible rejection of something it could not accept. Vomiting is not subtle; the system has decided the content has to come out and is not asking permission. The dream brings vomit when something in your life — a meal of bad news, a moral compromise, an environment that stopped agreeing with you — has been taken in past the point where the system can tolerate it. Vomit produced into a basin, in private, is the dream affirming that the rejection is being handled. Vomit that comes in a public place, with no warning, is the dream noting that the body has lost patience with how long the deliberate self was going to wait, and the rejection is now everyone's problem.