Well, after a hand of my own and one of kennyg's, where we both described our opponents as stations (and the play of the hand had some un-station-ish aspects), I thought I'd give my "definition" of what a calling station actually is.
There's one player whom I always think of when I use this term. His style had 2 characteristics that I thought were just the "paradigm" of a calling station: 1) He'd call any bet on any draw, 2) He'd bet big when he made his hand.
And I guess one might add: 3) Call a raise with any 2 cards close together (63o is worth calling) or any 2 suited.
Now, the thing is, in reality, even a "station" usually isn't quite this station-ish. And even this guy once actually check-raised me!!! He called my raise with T8o, flop came T8rag, and I had JJ. In this case, I did see him flinch when it came to him (he was sitting to my right), so I guess I should have known something was up. But I made my continuation bet anyway, and, bang... check-raise. That was really the only time I saw him play out of character, however. Pot-sized bet? call with straight or flush draw ALWAYS. Hand looks like a winner? Bet strong, raise, etc.
All very straightforward and predictable. And, if there's a flush or a straight out there and they bet, then believe it!
There are lots of players who have some station in them, however, but most have a few tricks as well. I wish I could characterize these guys a bit better (any suggestions?), but I thought I'd at least start by giving my example might at least be a good start. Any suggestions on defining nuances here would be much appreciated, however. There are definitely lots of station-ish players who throw you a little trickiness here and there.