Sideburn

Sideburns were a variant of facial hair; they were thick patches of whiskers on the sides of one's head.

The Third and Fourth Doctor both wore sideburns (TV: Spearhead from Space, TV: Planet of the Spiders) - the Fourth's were red even though the hair on his head was dark brown. (PROSE: The Drosten's Curse) The Tenth Doctor was delighted to see he had grown sideburns after his regeneration. (TV: Born Again) He kept them to the end of his life, (TV: The End of Time) though he was once temporarily aged to a point he lost them, and later, all of his hair. (TV: The Sound of Drums, Last of the Time Lords) His fourteenth self, who was almost identical to his tenth, was delighted to get his sideburns back.

The Tenth Doctor described the Fourth Doctor as being all "scarf and sideburns". (AUDIO: Out of Time)