\Con`trac*til"i*ty\, n.
1. The quality or property by which bodies shrink or
   contract.
2. (Physiol.) The power possessed by the fibers of living
   muscle of contracting or shortening.
Note: When subject to the will, as in the muscles of
      locomotion, such power is called voluntary
      contractility; when not controlled by the will, as in
      the muscles of the heart, it is involuntary
      contractility.