a hill: a rounded natural rise in the land, lower and gentler than a mountain
A hill is a rise in the ground, smaller and softer than a mountain. Hebrew almost always names it next to its larger partner, the mountain, so that the pair together sweep in the whole shape of the country: the high peaks and the low hills, everything in between understood.
The same plain word does three jobs. Most often it is simply scenery: the rise Moses climbs to watch a battle, the hills that skip like lambs and break into singing in the Psalms, the hills that will be leveled flat or will flow with plenty in the visions of the Prophets.
Because a hilltop was the obvious spot to raise an altar, the word also became the standard shorthand for open-air shrines. The Prophets return again and again to the phrase "on every high hill," and there it is never a scenic note but a charge of unfaithful worship. And because a hill is a natural landmark, the word often opens the name of a particular place, the hill of a named person or event.