Which, in a circular way takes us back to the OP's original question- what is "wine"?
Perhaps etymology might shed light on this subject.
English "wine" is, as many of you know, derived, via Old High German, from Latin "vinum". According to the OED, Latin derived the word via primitive - armenian *woiniyo.
This makes sense since the earliest winery was found in modern day Armenia, see Nat Geo article
here.
(also from OED) The word is related to many Semitic language words (Arabic, Ethiopic 'wain', Hebrew 'yayin', Assyrian 'înu').
In all languages, as in the Armenian cave, the word "wine" (and cognates) refer specifically to fermented grapes.
In English, it is not until 1398 that there is any definitive reference to another fermented fruit being called "wine." John Trevisa:
"Wyne ymade is ymade by crafte of good spicery & herbes. And it fareþ of þe wyn þat hatte Salinacum & of þe wyn þat hatte rosatum & Gariofilatum"
see also 1542 entry "All maner of wynes be made of grapes, excepte respyse, the whiche is made of a bery."
Thus, linguistically speaking, "wine" is only "wine" if it is from a grape.
personally speaking, if it ain't 'cider', 'beer', 'sake' or 'liquor', I call it wine. Even if its hoochy. Even grape wine can be hooch, look at Boone's Farm and Thunderbird.
Edit: OED= Oxford English Dictionary "wine" n.1, etymology, and sense 2. oed.com