I am not sure if there is a strict definition.
Your OS call is not bad but i think it is also to do with display hardware, graphics.
SO maybe a feature phone doesnt' have touch-screen, and menus based on it, but a low-end smartphone does?
How is an "entry-level smartphone" distinguished from what is today called a "feature phone"? It seems to me that the lines of distinction are blurring -- the one called "smartphone" runs Android 4.0, while the one called "feature phone" runs a simpler OS like Brew or Symbian.
Small screen, limited multi-media, less memory, etc. Does the market really need this to run Ice Cream Sandwich?
Smartphone commodization marches forward. The functionality of these devices as data terminals is rapidly becoming more important than their use as a telephone, potentially even at the low end. This meshes with the fact that in many countries a cell phone is the primary means of accessing the Internet. I'd be curious to hear what kind of BOM cost they are talking overall for these devices. Any ideas?