"Run" has many dictionary definitions such as "moving swiftly by foot". See Running, and "Run" in Wiktionary.
A run in a Stream or River is a fairly smooth flowing segment or part of the flow differentiated from a Pool where the water is deeper and slower moving, and a Rapid where the flow is shallower and more turbulent.
A run is a New Zealand term for a landholding corresponding to a ranch.
A run is a small enclosure used for the exercise of (normally caged) domesticated rodents such as rabbits and guinea pigs. This term typically refers to a small patch of grass.
Run is a term used commonly in Role Playing Games to flee a battle, not gaining any experience. Run options are often limited (such as not being able to run from boss battles or more powerful enemies, and costing the player money).