Leukorrhea (US) or leukorrhoea (Commonwealth) is a meical term that denotes a thick, whitish vaginal discharge. It is a natural defense mechanism the vagina uses to maintain it's chemical balance, as well as to preserve the flexibilty of the vaginal tissue. It may also result from inflammation or congestion of the vaginal mucosa. In cases where it is yellowish or gives off an odor, a doctor should be consulted since it could be a sign of an STD.