A large brightly colored bottle used for identification purposes so that American students can find other American students while abroad. Other uses include the transportion of liquids.
"Uh, hi, I couldn't help but notice your Nalgene... so where do you go to school?"
Someone who claims to possess or actually possesses a tremendous knowledge of the wilderness and has a well-traveled plastic water bottle - usually with stickers from various outdoor locations.
That dude was telling me some amazing stories about his six month backpacking trip in Patagonia. He such a nalgenius. And that BPA-free water bottle of his is sick - did you see the wear marks on it?