Christmas treen.1. An evergreen or artificial tree decorated, as with lights and ornaments, during the Christmas season.2. A device that consists of pipes and valves and caps a producing natural gas or oil well in order to control its flow. American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Christmas tree n 1. (Plants) an evergreen tree or an imitation of one, decorated as part of Christmas celebrations 2. (Plants) Also called: Christmas bush Austral any of various trees or shrubs flowering at Christmas and used for decoration 3. (Plants) another name for pohutukawa Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Christ?mas tree` n. an evergreen tree decorated at Christmastime with ornaments and lights. [1780?90, Amer.] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.