Meaning of reductio ad absurdum

re•duc•ti•o ad ab•sur•dum

Pronunciation: (ri-duk'tē-ō" ad' ab-sûr'dum, -zûr'-, -shē-ō"), [key]
— Logic. Logic.
  1. a reduction to an absurdity; the refutation of a proposition by demonstrating the inevitably absurd conclusion to which it would logically lead.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.