dilator dilator dilator or dilatator is a medical term with a number of uses, including: a surgical instrument or medical implement used to induce dilation, that is, to expand an opening or passage such as the cervix (see cervical dilator), urethra, esophagus, or vaginal introitus. a pharmacological treatment used to induce dilation, such as cervical dilation, vasodilation, or pupillary dilation. for example, a bronchodilator. a muscle which causes dilation of a part, for example, the iris dilator muscle or the dilator naris muscle. a 16th-century lithotomy dilator, used to expand the urethra for extraction of urinary stones