| aurora | (noun) an atmospheric phenomenon consisting of bands of light caused by charged solar particles following the earth's magnetic lines of force | - |
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| (noun) the first light of day | Synonyms: break of day, break of the day, cockcrow, dawn, dawning, daybreak, dayspring, first light, morning, sunrise, sunup |
| microradian | (noun) a unit of angular distance equal to one thousandth of a milliradian | - |
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| peroration | (noun) (rhetoric) the concluding section of an oration | - |
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| (noun) a flowery and highly rhetorical oration | - |
| proration | (noun) the proportional limitation of production or distribution of something (e.g. crude oil or natural gas) to some fractional part of the total capacity of each producer | - |
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| xeroradiography | (noun) radiography using X-rays and xerographic (rather than roentgenographic) techniques | - |
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