Defuse: To remove the fuse from (an explosive device). To make less dangerous, tense, or hostile. via The Free Dictionary
Discreet: Marked by, exercising, or showing prudence and wise self-restraint in speech and behavior, circumspect. Free from ostentation or pretension, modest. via The Free Dictionary
Discrete: Constituting a separate thing. Consisting of unconnected distinct parts. via The Free Dictionary
Descendant: A person, animal or plant whose descent can be traced to a particular individual or group. Something derived from a prototype, or earlier form. via The Free Dictionary
Descendent: Moving downward, descending. Proceeding by descent from an ancestor. via The Free Dictionary
Yep, just me Cathy thinking out loud about the letter "D".