The headword is aorist middle imperative of katadiaire/w. It is perhaps quoted from Psalm 47:14 LXX (katadie/lesqe ta\s ba/reis au)th=s, a passage much cited and commented on in Christian writers), though one should note that in Hesychius kappa1069 these are aorist infinitives -- the headword one perhaps quoted from Polybius 2.45.1.
cf. generally delta 913.