Last week, I ordered a pint of Gigantic's new beer, IPL, sight unseen. I was at a pub that listed nothing but the name. A few minutes later, the waiter dropped a glass of something pilsner-pale and conditioned-clear in front of me. I had assumed--correctly, it emerged--that the name of the beer stood for "India Pale Lager." The beer in front of me had almost nothing to do with IPA, though. Indeed, I later discovered that Ben and Van (brewmaster and master brewer) also call it a "Northwest pilsner," and it's a lot closer to a pils than anything to do with English or American ales. It's 5.6%, has a pilsner malt bill, and is, not unimportantly, a lager.
During that same session--possibly just after the arrival of the Gigantic--one of my friends complained that IPA no longer had any meaning at all. He ticked off the various offenses against a once-knowable style: black IPAs, white IPAs, lagered IPAs, session IPAs, fruit IPAs. (He actually ordered a rye and double IPA that night.) It had nothing to do with the original IPAs and has devolved into little more than a marketing gimmick, he argued reasonably.
As someone who has complained about this very phenomenon, I should have been sympathetic, but here's the thing: to the average drinker, slapping the word "India" on a label communicates a very specific, easily-understandable meaning. It's shorthand for "saturated in the flavors and aromas of American hops." Gigantic IPL, for all the ways it wasn't an IPA, instantly met the expectations I'd had--it was decadently perfumed and soaked in Simcoe and Citra hops.
Beer taxonomists and history prescriptivists miss this truth that is so obvious to the casual drinker. The qualities that separate the 19th century English originals--or the middle 20th century English or even late 20th century American versions--from these myriad permutations (Belgian, black, imperial, etc.) are vast. But that's because there's now a contemporary definition and it does a pretty good job of characterizing things.
Until something like thirty years ago, the hoppy beers typical in American brewpubs today did not exist. There were hoppy beers, but they didn't have the kind of hopping Americans now use--which is partly a function of the method but mostly a function of the hops themselves. And those qualities, begotten by vigorous kettle hopping and profligate late and dry-hopping of American hops, is what "India" (or "IPA" or "IP-whatever") now refers to. It's sort of like the catch-all term "Belgian," which means anything with vivid yeast character but can be applied to any imaginable style (except, I suppose, lagers). One of the great revelations of my foreign travel was to see that this shorthand was well-understood by breweries in the UK, Italy, and the Czech Republic. "American IPA" or "American-style" always meant super-hopped with American hops, whatever the beer style.
I've stopped overthinking this. Breweries want customers to know what the beer is going to taste like. If they attach the word "India" to it--whether it is just a hoppy pilsner or witbier or stout--customers know what they mean. It's pedantic to insist that there's something wrong with how this artifact of language has evolved.