The Collaborative International Dictionary of English v.0.48:

Viability \Vi`a*bil"i*ty\, n.
   The quality or state of being viable. Specifically:
   [1913 Webster]
   (a) (Law) The capacity of living after birth. --Bouvier.
       [1913 Webster]
   (b) The capacity of living, or being distributed, over wide
       geographical limits; as, the viability of a species.
       [1913 Webster]

WordNet (r) 3.0 (2006):

viability
    n 1: (of living things) capable of normal growth and development
    2: capable of being done in a practical and useful way

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "viability":
   acceptability, achievability, actability, activation, adequacy,
   admissibility, agreeability, animal spirits, animate existence,
   animation, attainability, being alive, birth, compassability,
   existence, feasibility, having life, immortality, life, lifetime,
   liveliness, living, long life, longevity, manageability,
   maneuverability, manipulatability, negotiability, operability,
   performability, practicability, practicality, reactivation,
   realizability, satisfactoriness, spriteliness, sufficiency,
   superability, surmountability, tenability, tolerability,
   unexceptionability, unobjectionability, viableness, vitality,
   vivacity, workability



Bouvier's Law Dictionary, Revised 6th Ed (1856):

VIABILITY, med. jur. An aptitude to live after birth; extra uterine life. 1
Briand. Med. Leg. 1ere partie, c. 6, art. 2. See 2 Sav. Dr. Rom. Append.
III. for a learned discussion of this subject.