observaˈtorial,a.rare—1. [f. as observatory a. + -al1.] Of or belonging to a (scientific) observer; of the nature of an observatory. 1816Faber Orig. Pagan Idol. I. ii. ii. 355 With respect to Cader-Idris,..the gigantic astronomer Idris, whose observatorial chair it is feigned to have been.