opposability

from The Collaborative International Dictionary of English v.0.48

Opposability \Op*pos`a*bil"i*ty\, n.
   The condition or quality of being opposable.
   [1913 Webster]

         In no savage have I ever seen the slightest approach to
         opposability of the great toe, which is the essential
         distinguishing feature of apes.          --A. R.
                                                  Wallace.
   [1913 Webster]