The Collaborative International Dictionary
Diffusibility
Diffusibility \Dif*fu`si*bil"i*ty\, n. The quality of being diffusible; capability of being poured or spread out.
Wiktionary
diffusibility
n. 1 (context physics of a gas or other fluid English) A measure of the speed of diffusion. 2 (context figuratively e.g. of a disease English) Capacity for spreading.