[dih-sahy-duh-buh l]
  1. capable of being decided.
  2. Logic. (of an axiom, proposition, etc.) having the property that its consistency or inconsistency with the axioms of a given logical system is determinable.

Origin of decidable

First recorded in 1585–95; decide + -able
Related formsde·cid·a·bil·i·ty, nounun·de·cid·a·ble, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for undecidable


  1. able to be decided
  2. logic (of a formal theory) having the property that it is possible by a mechanistic procedure to determine whether or not any well-formed formula is a theorem
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012