WordNet (r) 3.0 (2006):

DEd
    n 1: a doctor's degree in education [syn: Doctor of Education,
         EdD, DEd]

The Jargon File (version 4.4.7, 29 Dec 2003):

DED
 /D?E?D/, n.

    Dark-Emitting Diode (that is, a burned-out LED). Compare SED, LER, 
    write-only memory. In the early 1970s both Signetics and Texas instruments
    released DED spec sheets as AFJs (suggested uses included ?as a power-off
    indicator?).


The Free On-line Dictionary of Computing (30 December 2018):

DED

   Dark-Emitting Diode (that is, a burned-out LED).  Compare
   SED, LER, write-only memory.  In the early 1970s both
   Signetics and Texas instruments released DED spec sheets as
   AFJs (suggested uses included "as a power-off indicator").

   [Jargon File]