Apparently, it's a term used about people who commute or travel around a lot. In essence, we are "transit consumers" and therefore we're more likely to use retail outlets at railway stations or airports. The word was first coined by Fitch, the US design and business consultancy, a decade or so ago — it’s not really in common use by the general public.
I kind of like the word. However, I don't go a bundle on the world it describes. A strange world of tired and frustrated commuters, who are always in a hurry and therefore don't have the time to shop around; desperate to purchase a bite to eat as they travel because they skipped lunch; eager to buy a magazine or book to occupy their time on the train; determined to buy that last-minute present so that they have something to take home. The retailers respond by providing few choices and overpriced products to what is essentially a captive market.