What does D stand for?

Dominion Resources, Inc., of Virginia

daemon (e. g. inetd = internet daemon)

Daemon

A program that runs in the background and performs specific functions at certain times or in response to events.

Deciduous

Tree or shrub that loses its foliage during the winter. Trees that shed their leaves in fall or Shedding leaves at the end of the growing season.

Derated

An engine which is restricted to a cower output below its potential maximum.

Deuterium (also abbreviated as 2D or 2H)

discourse

normalized detectivity

David

Detective