Decongestant (noun)

1. A drug or medication used to reduce nasal congestion by narrowing the blood vessels in the nasal passages.
2. A substance that relieves nasal congestion by shrinking the blood vessels in the nasal passages.

Origin:

From de- + congest + -ant.

Examples:

1. The decongestant helped to clear her stuffy nose.
2. He took a decongestant before the flight to help with his sinus congestion.
3. The decongestant was administered to reduce the swelling of the nasal passages.
4. I always keep decongestants on hand for when I get a cold.
5. The decongestant was effective in relieving the patient's nasal congestion.