Panty dropping index. On a scae of one to do-me-now the likelihood and speed of an object or situation to cause a woman to remove her under-panties.
Ted just got done fighting a fire, that is a "do-me-now" on the PDI scale. *SPLOOSH!* panties off!
by penispaste March 01, 2014
2 more definitions
acronym - public display of intercourse. usually occurs at school, during a movie, when the teacher has the lights turned off and the students are allowed to lie about on the floor.
"Dude, I've been scarred for life. I saw Tony and Aimee doing PDI during that U.S. history movie."
by azer29 October 12, 2006
It means that you have a PhD in being really & officially gay ...
Just like Adam Sandler got a P.D.I.after that movie ( I Now Pronounce You Chuck and Larry )
by Mr.Small May 22, 2009