PCD stands for programmed cell death. This happens when a cell is in a state of poor health/disrepair, so release of special proteins (like cytochrome c - found in mitochondria) either from inside of the cell or by another cell, triggers an organized chain reaction of events, resulting in the degradation and destruction of proteins and nucleic acids inside the cell.
The genes responsible for the proteins that signal PCD are not working correctly in cancer cells.
Bob "Have you heard that cells can commit suicide?"
Pete "No"
Bob "This is also referred to as PCD, or apoptosis"
Pete "Is that going to be on the finals?"
Bob "Definitely!"
by dicAcielcunobiryxoeD June 10, 2008
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Pitch Circle Diameter.

Refers to the number of lug nuts in a wheel and the distance from one lug to the opposite end of the lug arrangement. This is also known as the bolt pattern.

Typically expressed in (Number of Lugs) X (Distance), for example, 5x4.50 (in inches) or 5x114.3 (in metric).
Mike: I'm looking for some new wheels for my BMW, what PCD would that be?

Paul: The bolt pattern for all BMW vehicles is always 5x120.
by Tatsumatic March 17, 2011
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CD-R with porn video/pic files burned onto them. Usually found in groups.
Person 1: Can I watch this in my dvd player?
Person 2: No, it's AVI, you have to watch it at your computer.
Person 1: but my familys dell is in the living room.
Person 2: Sux
by Thuggin' March 26, 2005
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Proper Creep Distance. Adj/verb. The appropriate distance at which you should walk behind an attractive chick. You should maintain this in order to get a good view but avoid alerting her to how hard you're staring at her fine ass and/or legs and making her run off like a spooked gazelle.
Man this hoe train I was PCD'ing downtown was so hot that I almost stepped on a sleeping bum.
by Jogler July 13, 2011
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Post Convention Depression

A depression after a USY convention, where all you can think about was the past days at your convention. You miss your kitahs, the dance, your mixers, the Torah song, other chapters, and the hookup you recently might of partaked in.
I've only been home for 6 hours, and my PCD is horrible. I miss my friends!
by DBUSY April 27, 2007
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Post Concert Depression
When you go to a lit concert and have fun, then you wake up the next morning feeling sad and missing it, while looking through all of the pictures and videos you took. This could last for a longer time
Friend: hey, I saw your snapchat story... how was the concert?
Me: It was lit, having serious pcd atm :(

Me: Remember the concert a few weeks ago?
Friend: aww stop, you're going to give me pcd.
Me: Yeah, I miss it too.
by iconic123 October 20, 2016
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