acute vaginitis or urethritis caused by infection with Trichomonas vaginalis, which does not invade the mucosa or the tissue but provokes an inflammatory reaction; infection is venereal or by other forms of contact; widespread infection in human populations is usually asymptomatic but may produce vaginitis, with vaginal and vulvar pruritis, leukorrhea with frothy watery discharge, and (rarely) purulent urethritis in males.