[gentile (n.) Look up gentile at Dictionary.com
“one who is not a Jew,” c. 1400; earlier “one who is not a Christian, a pagan” (late 14c.), from Late Latin noun use of Latin gentilis “of the same family or clan, of or belonging to a Roman gens,” from gens (genitive gentis) “race, clan” (see genus, and compare gentle).
The Latin adjective also meant “of or belonging to the same nation,” hence, as a noun, gentiles (plural) might mean “men of family; persons belonging to the same family; fellow countrymen, kinsmen,” but also “foreigners, barbarians” (as opposed to Romans), those bound only by the Jus Gentium, the “law of nations,” defined as “the law that natural reason establishes among all mankind and is followed by all peoples alike.”
The Latin word then was used in the Vulgate to translate Greek ethnikos (see ethnic), from ta ethne “the nations,” which translated Hebrew ha goyim “the (non-Jewish) nations” (see goy). Hence in Late Latin, after the Christianization of Rome, gentilis also could mean “pagans, heathens,” as opposed to Christians. Based on Scripture, gentile also was used by Mormons (1847) and Shakers (1857) to refer to those not of their profession. – etymonline]
Based on most of what’s stated here the word “Gentile” means “Nations” which would be an English translation for the word “Goyim”. Thus the word purely would mean “Non-Jew” when we as Jews use it. However, there is the ability to use the expression to allude to “pagans” even though that is not the strict meaning of the word.
I’m assuming that the Rabbi who made that statement distinguishing between “Gentiles” (pagans) and “Noahides” (believers in one G-d) was doing so in context of Halachah where a distinction many times exist, but often is misunderstood by laymen due to their not distinguishing between the two categories (“Gentiles” (pagans) and “Noahides” (believers in one G-d)). He was most likely trying to clarify that in Halachah the term “Gentile” is often referring to “Pagans”, not “Believers in one G-d”.