a valley: a deep, narrow, steep-sided ravine cut between hills or mountains
This is the word for a sharp gorge, the kind of cleft that drops away suddenly between high ground on either side. It is not the open, gently sloping vale that farmers plant (Hebrew has a separate word for that), nor a dry streambed: it pictures a deep fold in the land where two slopes pinch close and the floor lies far below the ridges.
Most of the time the word simply names such a place in the landscape, and the Bible uses it both for real terrain and as a vivid image. Because it suggests low, hidden, shut-in ground, it lends itself to scenes of danger and death (the shepherd's dark ravine in Psalm 23) and to pictures of leveling, where every deep valley is lifted up to make a smooth road.
The other common use is as the fixed first half of a place-name. A particular ravine gets a label and becomes the Valley of So-and-so: the Valley of Hinnom outside Jerusalem, the Valley of Salt south of the Dead Sea, the Valley Gate in the city wall named for the ravine it opened toward. In these the word still means an ordinary valley; it has just hardened into the name of one specific spot.