Congestion What does " Congestion " mean in a report or doctor's letter? In our medical dictionary, you will find a patient-friendly explanation of the meaning of this medical term. Looking for online definition of congestion in the Medical Dictionary? congestion explanation free. What is congestion? Meaning of congestion medical term. What does congestion mean ? Use the noun congestion to talk about over-crowding; this comes up most often when people talk about traffic. If there's unexpected congestion on your route to work, you'll be late. 3 meanings : 1. the state of being overcrowded, esp with traffic or people 2. the state of being overloaded or clogged with.... Click for more definitions.