What is the full meaning of YD? What does YD stand for?

YD stands for;

YD Yard
YD Young Democrats
YD Younger Dryas (prehistoric climate period)

YD Year-to-Date
YD Year Date (date on a stamp; philately)
YD Floating Crane (Non Self-Propelled)

YD Yankee Division (WWI; infantry division from New England)
YD Yaw Damper
YD District Derrick, Floating (US Navy)