[1] : The Collaborative International Dictionary of English v.0.48

aurora \auro"ra\, n.; pl. e. auroras, l. rarely used
   aurorae. l. aurora, for ausosa, akin to gr. ?, ?, dawn,
   skr. ushas, and e. east.
   1. the rising light of the morning; the dawn of day; the
      redness of the sky just before the sun rises.
      1913 webster

   2. the rise, dawn, or beginning. --hawthorne.
      1913 webster

   3. class. myth. the roman personification of the dawn of
      day; the goddess of the morning. the poets represented her
      a rising out of the ocean, in a chariot, with rosy fingers
      dropping gentle dew.
      1913 webster

   4. bot. a species of crowfoot. --johnson.
      1913 webster

   5. the aurora borealis or aurora australis northern or
      southern lights.
      1913 webster

   aurora borealis, i. e., northern daybreak; popularly called
      northern lights. a luminous meteoric phenomenon, visible
      only at night, and supposed to be of electrical origin.
      this species of light usually appears in streams,
      ascending toward the zenith from a dusky line or bank, a
      few degrees above the northern horizon; when reaching
      south beyond the zenith, it forms what is called the
      corona, about a spot in the heavens toward which the
      dipping needle points. occasionally the aurora appears as
      an arch of light across the heavens from east to west.
      sometimes it assumes a wavy appearance, and the streams of
      light are then called merry dancers. they assume a variety
      of colors, from a pale red or yellow to a deep red or
      blood color. the

   aurora australisis a corresponding phenomenon in the
      southern hemisphere, the streams of light ascending in the
      same manner from near the southern horizon.
      1913 webster
see also:
auroras aurorae aurora borealis aurora australis 

[2] : WordNet (r) 2.0

aurora borealis
     n : the aurora of the northern hemisphere syn: northern lights
see also:
northern lights 

Aurora Borealis >> A Words
Aurora Borealis, definition of term: Aurora Borealis
aurora+borealis_pag1.html

Aurora >> A Words
Aurora, definition of term: Aurora
aurora_pag1.html