aurora

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A luminous atmospheric phenomenon appearing as streamers or bands of light sometimes visible in the night sky in northern or southern regions of the earth. It is thought to be caused by charged particles from the sun entering the earth's magnetic field and stimulating molecules in the atmosphere.
2. n. The dawn.

Century Dictionary and Cyclopedia

1. n. The rising light of the morning; the dawn of day, or morning twilight.
2. n. [capitalized] In Roman mythology, the goddess of the dawn: called Eos by the Greeks. The poets represented her as rising out of the ocean in a chariot, her rosy fingers dropping gentle dew.
3. n. The aurora borealis or the aurora australis (the polar lights).
4. n. A reddish color produced by dyeing with arnotto.
5. n. In electricity, an electric glow-discharge, appearing at very high voltages and some what resembling the aurora borealis. It first appears as a blue glow at surfaces and especially at points; at higher electric pressures or voltages pink streamers issue, which gradually lengthen with increasing voltage until ultimately a disruptive spark occurs. See electric spark. Also called corona.
6. n. The length of time elapsing between successive maxima or minima of auroral displays, as the diurnal, the annual, the sun-spot, and the 55-year period. The last is possibly equivalent to 5 sun-spot periods. See auroral periodicity.

Wiktionary

1. n. An atmospheric phenomenon created by charged particles from the sun striking the upper atmosphere, creating coloured lights in the sky. It is usually named australis or borealis based on whether it is in the southern or northern hemispheres respectively.

GNU Webster's 1913

1. n. The rising light of the morning; the dawn of day; the redness of the sky just before the sun rises.
2. n. The rise, dawn, or beginning.
3. n. (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.
4. n. (Bot.) A species of crowfoot.
5. n. The aurora borealis or aurora australis (northern or southern lights).

WordNet 3.0

1. n. the first light of day
2. n. an atmospheric phenomenon consisting of bands of light caused by charged solar particles following the earth's magnetic lines of force
3. n. (Roman mythology) goddess of the dawn; counterpart of Greek Eos