n.; pl. Pessaries [ L. pessarium, pessum, pessus, Gr. pesso`s: cf. F. pessaire. ] (Med.) (a) An instrument or device to be introduced into and worn in the vagina, to support the uterus, or remedy a malposition. (b) A medicinal substance in the form of a bolus or mass, designed for introduction into the vagina; a vaginal suppository. [ 1913 Webster ]