Wiktionary
undercurve
n. The curve formed by the underside of something.
Usage examples of "undercurve".
Gently he bit the undercurve of her breast, using his teeth just enough to let her feel them but not enough to bring pain.
He even stopped scratching at the undercurve of his ample belly, where tangled hair met the lacings of his patched and wrinkled sea breeches.
More or less exactly halfway between the shadowed undercurves of her breasts and the second line of hair lay the puckered and babyish eyelid of the navel, itself the central point of the shallow convexity that now flattened out on to the hinges of the hips, where the skin was weak, and tender veins were disclosed .