Other forms: hillyer
Land that's hilly rises and falls with many hills. The hilly roads in eastern Kansas might surprise you, if you've always imagined the entire state being completely flat.
A hilly neighborhood requires walkers to trudge up steep slopes, and a hilly field is a picturesque backdrop for a farmer's exotic sheep to graze in. Anything that's hilly is marked with hills, or mounds of land that are smaller than mountains. The Old English source of both hilly and hill is hyll, from a Proto-Germanic root.