december

n. twelfth and final month of the Gregorian calendar

December is the twelfth and last month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days.December begins (astrologically) with the sun in the sign of Sagittarius and ends in the sign of Capricorn. Astronomically speaking, the sun begins in the constellation of Ophiuchus, which is the only zodiacal constellation that is not counted as an astrological sign, and ends in the constellation of Sagittarius.
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Noun
1. the last (12th) month of the year
(synonym) Dec
(hypernym) Gregorian calendar month
(part-holonym) Gregorian calendar, New Style calendar
(part-meronym) New Year's Eve, December 31

n. December, twelfth and final month of the Gregorian calendar

(n.)
The twelfth and last month of the year, containing thirty-one days. During this month occurs the winter solstice.
  

(n.)
Fig.: With reference to the end of the year and to the winter season; as, the December of his life.