Added 9 October 2026 dec noun Categories: TimePlacesUncommon Words noun ! Definition from WordNet 3.1, Princeton University. More about dec at Wordnik → Where our words come from → The last (12th) month of the year. (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. Related Words: decemberdeclinationjulfebcueercseptcemmicoctpres Back to today's word