Decay Posted on 7th November 201528th August 2020 by ThePD (The Project Definition) Decay means to become gradually damaged, worse, or less. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in General and tagged corrosion. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.