Nasal irrigation, also known as nasal lavage, is the act of flushing one's nasal cavity by pouring or injecting a liquid (usually salt water) into one nostril and letting it run out the other.  This can be done with a specialized pot or any number of syringes, squeeze bottles, and even electrically powered pumps marketed specifically for the purpose.  In addition to the obvious mechanical effect it can have on nasal congestion, practitioners of nasal lavage believe the practice clears out irritants, allergens, and pathogens that may have collected in the nasal cavity.
nasal irrigation