witness mark
n.— «Witness marks on the jack screws that drive the flaps and on other data indicate that Flight 801’s flaps had been placed in the landing setting of 30 deg., according to investigators.» —“Guam Probe Targets Weather, Altitude Alert” by James T. Mckenna Aviation Week & Space Technology Aug. 18, 1997. (source: Double-Tongued Dictionary)
Further reading
After our conversation about the expression dingle day, a term used by workers at a research station in Antarctica to denote bright, sunny weather, a listener offers a possible explanation for this term. It may derive from the idea of the skies...
Byron in Florence, South Carolina, is curious about his grandmother’s expression might as well, can’t dance, which she used when someone suggested an activity. This saying, as well as longer versions, are rooted in the idea of weather...