look up any word, like the eiffel tower:
 
1.
Or TD for short is a name to describe the amount of tards in a given area.

The TD scale ranges from from 0 to 100 where 0 is an empty building and 100 is so massive that only Chuck Norris could survive.

TD can be used either as an percentage or as arbitrary scale.
"God I traveled with the Metro today and the TD was massive like 80"

"I had a lovely vacation, the Tard Density was only around 5"
by uberEpicDonkey March 24, 2010