We refer to that as 'retching'

"I feel nauseous."

Bob, thank you for your comment and the link. Very useful.

Paul, that's interesting. This is a good discussion topic. I prefer to use "nauseated" for its meaning of "disgusted" - "I feel nauseated by all the political propaganda" - and for actually having been nauseated by something - "I felt nauseated by the thought of going to bed with her." For something that nauseates, I prefer to use the participle "nauseating" - "His obsequiousness is nauseating." I agree that nauseous can mean "affected with nausea; feeling inclined to vomit" (first meaning put forward by the Oxford Dictionaries) and "causing nausea". Thank you for the link.