congestion

Short definition from Wiktionary

Noun

1. 1
   The hindrance or blockage of the passage of something, for example a fluid, mixture, traffic, people, etc. (due to an excess of this or due to a partial or complete obstruction), resulting in overfilling or overcrowding: An accumulation or buildup, the act of gathering into a heap or mass.
2. 2
   The hindrance or blockage of the passage of something, for example a fluid, mixture, traffic, people, etc. (due to an excess of this or due to a partial or complete obstruction), resulting in overfilling or overcrowding: Blocking up of the capillary and other blood vessels, etc., in any locality or organ (often producing other morbid symptoms); local hypermic, active or passive.
3. 3
   An excess or accumulation of something: An excess of traffic; usually not a complete standstill of traffic, so usually not synonymous with traffic jam.
4. 4
   An excess or accumulation of something: An excess of mucus or fluid in the respiratory system; congestion of the lungs, or nasal congestion.
5. 5
   An excess or accumulation of something: Edema, water retention, swelling, enlargement of a body part because of fluid retention in tissues and vessels.