'external conductivity' definitions:

Definition of 'external conductivity'

From: GCIDE

Emissivity \Em`is*siv"i*ty\, n. Tendency to emission; comparative facility of emission, or rate at which emission takes place; specif. (Physics), the rate of emission of heat from a bounding surface per degree of temperature difference between the surface and surrounding substances (called by Fourier external conductivity). [Webster 1913 Suppl.]