When you are going down on a woman who hasn't had sex for a while. As a result, her v jay jay is filled with cobwebs, giving a fuzzy appearance. This fuzziness can cause your dick to be tickled often causing you to yell out "yabba-dabba-doo" like Fred Flintstone. First referenced in an obscure European film from the 1970's.
Tim- "Dude, how was that fuzzy fred flintstone last night?"