This is the 924th most frequent Italian word.
fiume
"Fiume" means "river" in English.
In this sentence, 'fiume' refers to a natural watercourse, indicating its primary geographic and physical meaning.
Il fiume scorre placidamente attraverso la valle.
The river flows placidly through the valley.
Here, 'fiume' is used metaphorically to describe a large, flowing group or crowd.
Un fiume di gente si radunò per la manifestazione.
A river of people gathered for the demonstration.
In this case, 'fiume' is used in the plural form to refer to the general concept of rivers, specifically tropical ones.