methotrexate definition
Freebase(0.00 / 0 votes)Rate this definition: Methotrexate. Methotrexate, abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid.