IPA: //ˌdiː.kənˈdʒɛs.tɪv//
KK: /diˈkɒnʤɛstɪv/
Relating to the reduction of congestion, especially in the nasal passages or other bodily areas.
The doctor prescribed a decongestive medication to help relieve my sinus pressure.
Decongestive → It is formed from "de-" (meaning down or away) and "congest" (from Latin "congestus", meaning to bring together or accumulate) and the suffix "-ive" (meaning having the nature of). The word "decongestive" refers to something that helps to reduce or relieve congestion by moving things away or breaking them apart.
Think of 'de-' meaning to move 'down' or 'away' and 'congest' meaning to 'bring together' — so a decongestive helps to move things away and relieve congestion.