Robin Good: If you are looking for free tools that can help you draft the design of your web site or application, look no further as this is a good collection providing ten wrireframing alternatives.
Definition of Wireframe:
A wireframe is a visual illustration of one Web page. It is meant to show all of the items that are included on a particular page, without defining the look and feel (or graphic design).
It’s simply meant to illustrate the features, content and links that need to appear on a page so that your design team can mock up a visual interface and your programmers understand the page features and how they are supposed to work.
Via Robin Good