On the side that is away from the axis or central line, usually on the underside
The lobule margins, furthermore, are arched away from the lobe, with the consequence that (when fully inflated) the abaxial leaf surface forms the interior lining of the lobule.
A direction perpendicular to an axis or the coordinate that measures displacement in such a direction
facing away from the axis of an organ or organism; "the abaxial surface of a leaf is the underside or side facing away from the stem"