Source : Webster's Revised Unabridged Dictionary (1913)

Earthlight \Earth"light`\, n. (Astron.)
   The sunlight reflected from the earth to the moon, by which
   we see faintly, when the moon is near the sun (either before
   or after new moon), that part of the moon's disk unillumined
   by direct sunlight, or ``the old moon in the arms of the
   new.''