Christmas tree

One of the most popular traditions associated with the celebration of Christmas, the Christmas tree is normally an evergreen conifer tree that is brought in the house or used in the open, and is decorated with Christmas lights and colourful ornaments during the days around Christmas.

Other meanings

• For students, to Christmas tree a test (specifically a computer-graded multiple choice test) is to fill in the answer sheet randomly, or in such a way as to form a design. Reasons for Christmas treeing a test include boredom, rebellion, and desperation (for students who are not prepared for the test). The name (an example of "verbing") comes from one popular pattern, which resembles a Christmas tree.
• Drag racing also has what is called a Christmas tree, so named because of the large number of lights that it has (and the branches which the lights are on). Each side (because drag racing is a contest between two vehicles) of the christmas tree has seven lights: two small yellow lights at the top and then in this order below them: three larger lights, green, and then finally a red light. The christmas tree as a whole is used to count down to the start so that the drivers can accurately judge the start.
• In computer networking jargon, a Christmas tree packet is a packet with all the options turned on.
• In petroleum engineering, the christmas tree is the valve assembly that connects to the top of the production or injection tubing, and interfaces to the flowline. It is attached to the well head, but it is a separate subsystem; the wellhead provides a mechanical and hydraulic interface to the various casing strings. There are several different designs of christmas tree, depending on well service and pressure, but they will typically include safety valves, choke valves, sampling points and chemical injection points.
• On the British railway network, a christmas tree is a locomotive or item of rolling stock which sits in a yard and is robbed of parts for use as spares as and when necessary.