1. Do a search
2. Notice an interesting result only somewhat related to your actual search.
3. Search on the new term.
4. goto 2.
Following interesting results from a given search to the point of getting lost in interesting results from search engines for hours. Often results in porn results withing a Kevin Bacon step envelope.
Search: how to get cat urine stains out of a leather couch.
You: "Wow, I've never heard of THAT fetish, I'll just search on it to find out more..."
and aawway you go! You've just started a tangential search.