Magnetic permeability

from The Collaborative International Dictionary of English v.0.48

Permeability \Per`me*a*bil"i*ty\, n. [Cf. F.
   perm['e]abilit['e].]
   The quality or state of being permeable.
   [1913 Webster]

   {Magnetic permeability} (Physics), the specific capacity of a
      body for magnetic induction, or its conducting power for
      lines of magnetic force. --Sir W. Thomson.
      [1913 Webster]