Overcrowded means holding far more people than it should. An overcrowded train, overcrowded housing, overcrowded prisons.
It is a defined term in housing law, where an overcrowded home is measured against room and floor space standards. Overcrowding is a leading factor in the spread of infection. Note that the over- means excessively, and that crowded on its own carries no judgement.
1adjectiveovercrowdedHolding far more people than it should.
“The overcrowded bus was so full that people were standing on the steps.”
overcrowded is a quality of excess occupancy.
From over- + crowded.
Etymology from Wiktionary, CC BY-SA