re·duc·ti·o ad ab·sur·dum (r?-d?k?t?-? ?d ?b-sûr?d?m, -zûr?-, -sh?-?)n. pl. re·duc·ti·o·nes ad absurdum (-??n?z, -n?s) Disproof of a proposition by showing that it leads to absurd or untenable conclusions.[Medieval Latin reducti? ad absurdum : Latin reducti?, a bringing back, reduction + Latin ad, to + Latin absurdum, absurdity, from neuter of absurdus, absurd.]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.reductio ad absurdum (r??d?kt??? æd æb?s??d?m) n1. (Logic) a method of disproving a proposition by showing that its inevitable consequences would be absurd2. (Logic) a method of indirectly proving a proposition by assuming its negation to be true and showing that this leads to an absurdity3. application of a principle or proposed principle to an instance in which it is absurd[Latin, literally: reduction to the absurd]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014re?duc?ti?o ad ab?sur?dum (r??d?k ti?o? ?æd æb?s?r d?m, -?z?r-, -?i?o?) n. a reduction to an absurdity; the refutation of a proposition by demonstrating that its logical conclusion is absurd. [1735?45;