What does dropped d mean?

dropped d meaning in Urban Dictionary

another electric guitar tuning where least expensive string is tuned down one whole-step. Common in most types of rock. Makes it much simpler to try out an electrical chord; the guitarist can easily lay one finger throughout the cheapest three strings. Seemed down upon for its center, but powerful in the possession of of a talented guitarist (instances: Killing within the title by Rage contrary to the device).Often misspelled 'drop D' as a result of the assimilation for the d at the end of 'dropped' and also the D at the beginning of 'D'.