Pronunciation: (a-ROW-ma-tays in-HIB-it-er) A medication that prevents the formation of estradiol, a female hormone, by interfering with an aromatase enzyme. Aromatase inhibitors are used as a type of hormone therapy for postmenopausal women who have hormone-dependent breast cancer. Examples of aromatase inhibitors include anastrozole (brand name: Arimidex), letrozole (brand name: Femara), and exemestane (brand name: Aromasin).