| Noun | 1. | Dec - the last (12th) month of the year Gregorian calendar, New Style calendar - the solar calendar now in general use, introduced by Gregory XIII in 1582 to correct an error in the Julian calendar by suppressing 10 days, making Oct 5 be called Oct 15, and providing that only centenary years divisible by 400 should be leap years; it was adopted by Great Britain and the American colonies in 1752 December 31, New Year's Eve - the last day of the year Christmas Day, Dec 25, Xmas, Christmas - a Christian holiday celebrating the birth of Christ; a quarter day in England, Wales, and Ireland Christmas, Christmastide, Christmastime, Noel, Yule, Yuletide - period extending from Dec. 24 to Jan. 6 Gregorian calendar month - a month in the Gregorian calendar mid-December - the middle part of December |
| 2. | dec - (astronomy) the angular distance of a celestial body north or to the south of the celestial equator; expressed in degrees; used with right ascension to specify positions on the celestial sphere astronomy, uranology - the branch of physics that studies celestial bodies and the universe as a whole angular distance - the angular separation between two objects as perceived by an observer; "he recorded angular distances between the stars" |