The build-up of a static charge, typically through a physical means, that creates a voltage differential between objects. This voltage differential usually results in a large discharge when the objects come together, either causing pain or destruction. A tricky part of that static discharge is that sometimes the discharge isn’t even noticeable but it can still cause damage to electronics.
Static electricity is accumulation of charge. Electric charges not in motion.
Grob’s Basic Electronics, 11th Edition by Mitchel E. Schultz