* Decongest: This is a verb meaning to relieve congestion, usually referring to the reduction of swelling or blockage in the nasal passages, sinuses, or other parts of the body.
* Discongest: This is a less common and arguably less correct spelling, but it also implies relieving congestion.
Here's an example:
* "I took a decongestant to help clear my stuffy nose."
If you can provide more context about where you encountered this term, it might be easier to understand what was intended.