ta·mox·i·fen 
(tə-mŏksə-fĕn)
(tə-mŏksə-fĕn)n.
A drug that is a selective estrogen receptor modulator, C26H29NOS, used in the form of its citrate primarily to treat breast cancer in women whose tumors are estrogen-dependent and to prevent breast cancer in high-risk women.
[T(RANS)- + AM(INO)- + alteration of OXY- + alteration of PHEN(OL).]