Congested means overly crowded or clogged up, so full that movement becomes slow or difficult. When a highway is congested during rush hour, cars pack together and barely inch forward. When your nose is congested during a cold, mucus blocks your nasal passages and makes breathing difficult.

The word captures that frustrating feeling of things being jammed up when they should flow freely. A congested airport has too many flights trying to use too few runways. A congested city neighborhood might have narrow streets overwhelmed by traffic, delivery trucks, and pedestrians all competing for space.

You can think of congestion like trying to pour water through a funnel that's partially blocked: everything backs up and slows down. Traffic congestion costs Americans billions of hours each year sitting in cars going nowhere. Nasal congestion makes your voice sound funny and can keep you awake at night.

The opposite of congested is clear or flowing freely: traffic moves smoothly, ideas flow easily in conversation, or you breathe deeply without any blockage. When something becomes less congested, we say it's clearing up or becoming decongested.