That's where you take a dump in a box, wrap it and put it under the tree. The best way to accomplish this to attend a Christmas party, bring a real gift and let every body know that it is yours so they will associate you with that gift. Then slip the Brown Santa under the tree without anybody watching.
This can be done at any party or celebration such as a birthday party or wedding, and with any inappropriate gift: vibrators, gay porn, roadkill and cremated remains.
You should have see the boss' face when he opened a Brown Santa.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.
British slang for a scientist or technical expert, esp . when the speaker is not certain of the expert’s specific field of study. Not necessarily derogatory, but typically used by persons without a technical background. In the US, the equivalent would be “egghead”, “squint”, or “geek.”
Origin of the word is unknown. Started sometime in World War 2. Given the typical evolution of British slang, could easily have started because what these experts did was confusing or “baffling” to the common person.