upstream
adj. B2 Upper Intermediate US //ˈəpˈstɹim// UK //ʌpstɹˈiːm// up·stream
adj. moving or located against the flow of a river. You can also use it to describe things that happen earlier in a process.
adj. situated or moving in the direction opposite to the flow of a stream or river; by extension, relating to the earlier stages of a production or biological process.
The salmon swim upstream to lay their eggs.
The environmental agency took water samples from the upstream section of the river to find the source of the pollution.
From up- + stream.
Usage
Can be used as both an adjective and an adverb without changing form.