Wadi: A steep-sided valley containing an intermittent stream in an arid region.

Warping: In tectonics, refers to the gentle, regional bending of the crust, which occurs in epeirogenic movements.

Water mass: A mass of water that fills part of an ocean or lake and is distinguished by its uniform physical and chemical properties, such as temperature and salinity.

Water table: A gently-curved surface below the ground at which the vadose zone ends and the phreatic zone begins; the level to which a well would fill with water.

Wave-cut terrace: A level surface formed by wave erosion of coastal bedrock to the bottom of the turbulent breaker zone. May appear above sea level if uplifted.

Wavelength: The distance between two successive peaks, or between troughs, of a cyclic propagating disturbance.

Wave steepness: The maximum height or amplitude of a wave divided by its wavelength.

Watt steam engine:was the first type of steam engine to make use of steam at a pressure just above atmospheric to drive the piston helped by a partial vacuum.

Weathering: The set of all processes that decay and break up bedrock, by a combination of physically fracturing or chemical decomposition.