'Externality' definitions:

Definition of 'externality'

From: WordNet
noun
The quality or state of being outside or directed toward or relating to the outside or exterior; "the outwardness of the world" [syn: outwardness, externality] [ant: inwardness]

Definition of 'Externality'

From: GCIDE
  • Externality \Ex`ter*nal"i*ty\, n. State of being external; exteriority; (Metaph.) separation from the perceiving mind. [1913 Webster]
  • Pressure or resistance necessarily supposes externality in the thing which presses or resists. --A. Smith. [1913 Webster]