To stream downward.
"The water cascaded downstream from the rocky ledge into the pool below."
in the direction of a stream's current
"The boat drifted downstream, carried effortlessly by the river's current toward the wide valley below."
Lower down, in relation to a river, stream or flow of fluid
"The fish swam downstream toward the mouth of the river."
In plain English: Downstream means located further along the direction that water flows, such as downstream from where you jumped into the river.
"The factory is located downstream from our neighborhood, so we worry about its pollution affecting the river water."
Usage: Use downstream as an adjective when describing something located further along the direction that water flows. It is often paired with upstream to indicate relative position within a current system rather than just physical height.
away from the source or with the current
"The fish swam downstream, moving away from the river's source and with the flow of the water."
Following the path of a river or stream
"The fish swam downstream toward the open ocean."
In plain English: Downstream means moving away from where something started, usually toward its end point or final destination.
"The fish swam downstream with the current."
The word downstream is a straightforward combination of the prefix down- and the noun stream. It has been used since at least the late 16th century to describe anything flowing or moving in the direction of a current's lower course.