yeah 3 lines would be cool,
You can suggest it at the developer's corner. But I think it's pretty hard. Normally the space of the progress bar is used for definitions. Three lines would mean changing the whole formatting of the kindle reading screen.
(I remember one request to toggle the progress bar, which i believe still isn't possible)
Maybe it's easier to change the font size of the pop up definitions.
Or when using the kindle 3 always make the definiton pop up at the top of the page and simultaneously let the next 2 lines of the definition pop up at the bottom of the page.
