The nickname for a top navigation menu that uses a string of section names to identify where you are. For example, when searching for cell phone product reviews on CNET.com, you will see the following "breadcrumbs" just beneath the top level navigation:
> Home > Reviews > Cell Phones and Accessories > All Cell Phones
Likened to the practice of leaving breadcrumbs behind you when you go hiking on a new trail or wandering through the wilderness, these top navigation links help you find your way back to where you started by following them in reverse order.
This expression is also used as a verb, as in "we can breadcrumb this section so we don't have to pile up content in the left nav."