资料来源 : Webster's Revised Unabridged Dictionary (1913)

   {Dead letter}.
       (a) A letter which, after lying for a certain fixed time
           uncalled for at the post office to which it was
           directed, is then sent to the general post office to
           be opened.
       (b) That which has lost its force or authority; as, the
           law has become a dead letter.

   {Dead-letter office}, a department of the general post office
      where dead letters are examined and disposed of.

   {Dead level}, a term applied to a flat country.

   {Dead lift}, a direct lift, without assistance from
      mechanical advantage, as from levers, pulleys, etc.;
      hence, an extreme emergency. ``(As we say) at a dead
      lift.'' --Robynson (More's Utopia).

   {Dead line} (Mil.), a line drawn within or around a military
      prison, to cross which involves for a prisoner the penalty
      of being instantly shot.

   {Dead load} (Civil Engin.), a constant, motionless load, as
      the weight of a structure, in distinction from a moving
      load, as a train of cars, or a variable pressure, as of
      wind.

   {Dead march} (Mus.), a piece of solemn music intended to be
      played as an accompaniment to a funeral procession.

   {Dead nettle} (Bot.), a harmless plant with leaves like a
      nettle ({Lamium album}).

   {Dead oil} (Chem.), the heavy oil obtained in the
      distillation of coal tar, and containing phenol,
      naphthalus, etc.