Valley n. : The space inclosed between ranges of hills or mountains; the strip of land at the bottom of the depressions intersecting a country, including usually the bed of a stream, with frequently broad alluvial plains on one or both sides of the stream. Also used figuratively.

Valley n. : The place of meeting of two slopes of a roof, which have their plates running in different directions, and form on the plan a reentrant angle.

Valley n. : The depression formed by the meeting of two slopes on a flat roof.

Example:
How long can Valley Fever stay dormant in a greyhound before causing real heath problems?

Taxonomy
valleys, glacier, shoulders, river valleys, Scotland, characteristic, U-shaped valley, villages, ice, slope, the Alps, U-shaped valleys, erosion, broad shoulders, free encyclopedia, rivers, Rift valleys, glen.

Defination from the web:
valley in the Mount Hood Wilderness showing a characteristic U-shape, the bottom's rocky 'rubble' accretion and the broad shoulders ... A deep, narrow valley is known as a coomb (also spelled combe or coombe) ...