In classical terms, a G dominant 7th?

No, it would be called a D7th. If clarification is needed, one could add, "the dominant 7th chord of the key of G."

If you refer to it as a "G dominant 7th," the next thing you'll hear from a classical musician will be "Wait a minute, wait a minute!" followed by a request for clarification of which key you're talking about, G or D.

I'm not making this up. I've had two years of music theory at the University of Washington School of Music, two more years at the Cornish College of the Arts (a performance arts conservatory in Seattle), and a year of private theory and composition study with Mildred Hunt Harris.

Music theory is quite systematic, as is the terminology. But it can become exceedingly confusing when one person who doesn't know much about it tries to explain it to others who are equally befuddled, making up terminology as they go along.

There are books on the subject!

Don Firth