Hi, ethic. Strangely enough, I'm just about to upload a lesson with a 'walking bass'. It means that the bass line sort of walks its way through a series of notes (most often chord tones) rather than sit on one note like the root, or alternate between two, usually the root and fifth. The bass becomes more of a melodic instrument. It's most often heard in jazz.
I should have that lesson up by tomorrow. It shows one example of a 'walking bass'. I think I did one a while back too ... yes, I did.
Here.
Here's wikipedia's definition:
In music, a walking bass is a bass accompaniment generally consisting of unsyncopated notes of equal value, usually quarter notes (known in jazz as a "four feel").