Washington, D.C., formally the District of Columbia and commonly referred to as "Washington", "the District", or simply "D.C.", is the capital of the United States.

Based on this passage, what do dc stand for in washington dc? Let's think fast. Stream of consciousness:
The relevant sentence in the passage is: Washington, D.C., formally the District of Columbia and commonly referred to as "Washington", "the District", or simply "D.C.", is the capital of the United States. So the final answer is District of Columbia.