What is a grognard?

In the Napoleonic era, a grognard was an old soldier. In modern times, it's come to mean an old gamer. I first encountered the term when my pal SC directed me to the "Grognardia" RPG website more than a decade ago. These days, I can't hear it without thinking of the wonderful RPG podcast "The Grognard Files". I like grognard as a descriptor because it sounds sort of curmudgeonly and also contains the word "grog". Mmmm...grog.