"Mucous" refers to a slimy substance that our body produces, like the stuff that comes out of our nose when we have a cold. It helps keep our body moist and protects it from germs. Full definition
In both speech and singing, we produce sustained vowel sounds by using vibrations of our vocal folds — small flaps of mucous membrane in our voice box (or Adams apple)-- that periodically interrupt the airflow from the lungs. (scientificamerican.com)
Please make sure to add a carrier oil to your homemade capsules to reduce the risk of mucous membrane irritation in your digestive system. (virginiageorge.com)
And for the record, a secure mucous plug in your cervix separates your amniotic sac and uterus from the rest of the world — including your partner during penetration. (whattoexpect.com)