Wiktionary
n. A substance that blocks the production or utilization of estrogens, or inhibits their effects.
Wikipedia
An antiestrogen is a substance that blocks the production or utilization of estrogens, or inhibits their effects. Estrogens are the family of hormones that promote the development and maintenance of female sex characteristics.
Although aromatase inhibitors could be considered antiestrogens by some definitions, they are often considered to be a distinct class. Aromatase inhibitors reduce the production of estrogen, while the term "antiestrogen" is usually reserved for agents reducing the response to estrogen.
Hot flashes, osteoporosis, breast atrophy, and vaginal dryness can be side effects of antiestrogens.
Usage examples of "antiestrogen".
Estrone acts as an antiestrogen, stopping the full action of estradiol.