Axial intelligibility indexes the degree to which the number of immediate connections a line has is a reliable guide to the importance of that line in the system as a whole (namely, it is a correlation between axial connectivity and axial global integration). A strong correlation, or ‘high intelligibility’, implies that the whole can be read from the parts.
Hillier, B., Burdett, R., Peponis, J., Penn, A. (1987), Creating Life: Or, Does Architecture Determine Anything? Architecture et Comportement/Architecture and Behaviour , 3 (3) 233 – 250. pp.237