Atrophic vaginitis: Thinning of the lining (the endothelium) of the vagina due to decreased production of estrogen. This may occur with menopause. Vaginitis means inflammation of the vagina, the muscular canal extending from the cervix to the outside of the body. Aside from atrophic vaginitis, there are a number of other types of vaginitis. Vaginitis may, for example, be caused by a fungal infection leading to itching or burning and a discharge.