[au.ro.ra] n, pl auroras or au.ro.rae [L--more at east] (14c) 1: dawn
2. cap: the Roman goddess of dawn--compare eos
3: a luminous phenomenon that consists of streamers or arches of light appearing in the upper atmosphere of a planet's magnetic polar regions and is caused by the emission of light from atoms excited by electrons accelerated along the planet's magnetic field lines -- au.ro.ral adj -- au.ro.re.an adj