| 
 | 
Definition of Reductio ad absurdum
1. Noun. (reduction to the absurd) a disproof by showing that the consequences of the proposition are absurd; or a proof of a proposition by showing that its negation leads to a contradiction. 
| 
 | 
1. Noun. (reduction to the absurd) a disproof by showing that the consequences of the proposition are absurd; or a proof of a proposition by showing that its negation leads to a contradiction.