Nausea n. : Seasickness; hence, any similar sickness of the stomach accompanied with a propensity to vomit; qualm; squeamishness of the stomach; loathing.

Example:
What's the difference between Nausea due to pregnancy and due to gastritis?

Taxonomy
Nausea, nausea and vomiting, symptom, Mild nausea, Causes of nausea, free encyclopedia, Articles with unsourced statements, Treatment, drugs, digestive system, body, motion sickness, movement, 2007-08-02, Doug Wamble, pregnancy, stomach flu, Viral hepatitis.

Defination from the web:
Nausea is not a sickness, but rather a symptom of several conditions, many of which are unrelated to the stomach. Nausea is often indicative of an underlying condition elsewhere in the body. ... Doxylamine is the drug of choice in pregnancy-related nausea. ...