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]

Try this search on Wikipedia, OneLook, Google

Nearby terms:

DEC Wars « DECwindows « DECwrite « DED » dedicated line » deductive database » deductive tableau