cf. generally delta 1105 for a similar headword plus gloss. (Eustathius, in fact, has all four words together.) In the present instance too, it seems, the headword is neuter nominative/accusative, though here it might instead be masculine accusative. In any event it has the same glossing in other lexica and must be quoted from somewhere, probably poetry (cf. Anthologiae Graecae Appendix, Problems and Riddles 79.74.1, di/korsos ei)mi/).
The -korsos part of the compound is probably related to the noun ko/rsh 'forehead/jaw/temple' (kappa 2110), but note also lexicographic korso/s = kormo/s 'log/oar/tree-trunk'; possibly, therefore, the application of dikorsos may extend to vegetation (a tree with two trunks) or to a boat with two oars.