Choanal: Pertaining to the choana, the passageway from the back of one side of the nose to the throat. The choana is shaped like the opening of a train tunnel in a mountain which then opens into the space called the nasopharynx. The choanae must be open to permit breathing through the nose. Choanal atresia is blockage of the choanal passageway while choanal stenosis is narrowing of that passageway. From the Greek choane (a funnel). The word choanal is pronounced co-anal but it has nothing to do with the anus.