dorsal

adjective

(L. dorsum: the back) Pertaining to the back, to the surface turned away from the axis, as in the lower surface of a leaf; abaxial; of a lateral organ, (relating to the side) facing away from the axis, i.e. the 'back'; of a thallus, facing away from the substratum; abaxial. Dorsal for bivalves: Toward the hinge and umbo. Cf. ventral.