Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "un-andgitfull." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 732.
;adj. Not intelligent, without understanding :-- Unondgetfulle insensati, Ps. Surt. ii. p. 195, 11. Ðæt ða andgytfullan mid worda láre tó Godes willan gemyngode sýn and ða unandgytfullan mid gódum dǽdum getrymede ut capacibus discipulis mandata Domini verbis proponat, et simplicioribus factis suis divina precepta demonstret, R. Ben. 11, 16. Ðǽm unandgytfullum (infirmis intellectibus) ðæt gástlíce angyt is earfoþe tó understandenne, 66, 19.