adj. describing a set for which there exists an algorithm that will determine whether any element is or is not within the set in a finite amount of time.
the GNU version of the Collaborative International Dictionary of English
adj. Capable of being decided; determinable.
The Century Dictionary and Cyclopedia
That may be decided.
Word Usage
"A theory T is defined to be decidable if there is an effective procedure of deciding whether any given sentence s belongs to T, (where an 'effective procedure' is generally defined to be a finitely-specifiable sequence of algorithmic steps)."