What is "Roadkill"?

["Richard H. Overman" <sunset_village@compuserve.com>]

    Hi, again, list people of all nations.
    I looked up the 1973 Square that's for sale for $20,000 on the owners
Web page and it showed a photo of something being spread over the floor pan
area under the carpet that they referred to as Roadkill.  Is it some kind
of soundproofing or what?
    The web address is:   www.knowitallproductions.com/vw/index.shtml    if
you want to see what I am writing about.

     --Leah Wegener,  '63 Squareback (finally got the headlights in the
fiberglass fenders--what a royal pain that was!!!)