meth·o·trex·ate (m?th??-tr?k?s?t)n. A folate antagonist, C20H22N8O5, that inhibits DNA synthesis and is used to treat psoriasis, certain cancers, and some inflammatory diseases such as rheumatoid arthritis. It is sometimes used in combination with misoprostol to induce abortion in early pregnancy.[methotre- (probably shortening and alteration of methylaminopterin, one of its chemical names : methyl + aminopterin) + perhaps (o)x(y)- + -ate.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.methotrexate (?m?????tr?kse?t; ?mi????-) n (Pharmacology) an antimetabolite drug used in the treatment of certain cancers. Formula: C20H22N8O5Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014meth?o?trex?ate (?m?? o??tr?k se?t) n. a toxic folic acid analogue, C20H22N8O5, that inhibits cellular reproduction and is used in the treatment of psoriasis and certain cancers. [1950?55; metho (xy)- + trexate, of unclear derivation] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.