This article appears to be a dictionary definition.
Fairy riding (Scottish Gaelic: marcachd shìth/a' mharcachd-shìth/na marcachd-shìth) was a term used for a kind of paralysis found in livestock in Scotland. It occurred in the spine of sheep, cows and horses, and was attributed to fairies riding on them.
It can be compared to elf-shot, where it was thought that animals had been shot by fairies.
- This article incorporates text from "Dwelly's [Scottish] Gaelic Dictionary" (1911). marcachd-shìth