Sloping, a.
Inclining or inclined from the plane of the horizon, or from a horizontal or other right line; oblique; declivous; slanting. -- Slop"ing*ly, adv. The sloping land recedes into the clouds. Cowper.
Shades of meaning
Fernald lists sloping only as an antonym, under horizontal.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given