What is the substantial evidence rule, move-over?

'The substantial evidence rule, move-over, has been highly developed and refined as a standard of . . . judicial review of the findings of administrative agencies. Thus absorbing it as one kind of gross error which permits review of the administrative settlement of public contract disputes is eminently practical.' (Clack v. State of California ex rel. Dept. Pub. Wks. (1969) 275 Cal.App.2d 743, 748, 80 Cal.Rptr. 274, 277.)