To cause an area or space to become overcrowded or blocked. The accident on the highway congested the traffic for miles.
To cause a part of the body to fill with fluid or blood, leading to swelling or blockage. The cold virus can congest the nasal passages, making it difficult to breathe.
To become overcrowded or blocked. During the summer tourist season, the tiny streets often congest with visitors.
To become filled with fluid or blood, causing swelling or blockage. Her sinuses congest rapidly whenever she’s exposed to pollen.