Unique. Peculiar; something that on account of its peculiar construction or arrangements stands out beyond the others.
Universal. Everywhere; all over the world.
Undulate. To move up and down; a wave-like motion.
Utility. Of use; to take advantageous use of.
Unstable. Not having anything permanent; in a ship in flight one that will not ride on an even keel, and is liable to pitch about.
Vacuum. Where air is partly taken away, or rendered rarer.
Valved. A surface which has a multiplicity of openings with valves therein, or, through which air can move in one direction.
Vaunted. To boast concerning; to give a high opinion.
Velocity. Speed; the rate at which an object can move from place to place.
Vertical. A line running directly to the center of the earth; a line at right angles to the surface of water.