selective estrogen receptor modulator
an estrogen-like drug that has some, but not all, of the actions of estrogen. For example, raloxifene is classified as a SERM because it acts like estrogen in some parts of the body (for example, helping prevent bone loss) but blocks the effects of estrogen in others (for example, it helps stop breast cells from using estrogen). Tamoxifen and toremifene are also SERMs. See also estrogen, uterus.