1.To jerk your hand up in a very fast motion.
2.Used to get a persons attention.
3. Also look in the opposite direction of the person, Do the "shady wave" and hunch your back.
4. Can be done repeatedly for an extended effect.
Mainly used in the town of Shenandoah PA.
Used as a verb: Wow that creep just shady waved me.
Used as a noun: Stop giving people the shady wave.