I have been recently blessed with several free Starbucks coffee cards. While in line, I have overheard many people ordering a drink called a red eye, which is not on the menu. Given that I understand the meaning of the term from airplane related adventures, I assumed this had to be a super strong espresso drink.
I came across several good definitions, one of which was hilarious and I had to share:
Red Eye (n.) -- Someone who can 'drink' (i.e., choke down) a Red Eye deserves your respect. This drink is basically a cup of coffee (already well caffeinated) with either one, two, or three espresso shots added for good measure. People that drink these are either clinically dead and need resurrection, or are writing a doctoral thesis or something equally mind-numbing. You may want to think twice before ordering this drink.
The drink has also been defined by Wikipedia. Apparently, the red eye is the equivalent of Dunkin Donuts' Turbo drink, if that is even still available.