Definitions

1. adverb

extending or located in the direction of the flow of a river, especially from the point of origin to the sea

“The raft drifted downstream, picking up speed.”

2. noun

the part of a river or stream that flows away from the source, especially towards the sea

“They went on a downstream hike along the riverbank.”

3. preposition

moving or located in the direction of the flow of a river or other fluid

“The water flowed downstream into the ocean.”