Real Dictionary

reverse osmosis in American English
a method of extracting essentially pure, fresh water from polluted or salt water by forcing the water under pressure against a semipermeable membrane, which passes the pure water molecules and filters out salts and and other dissolved impurities
noun: the process in which pure water is produced by forcing waste or saline water through a semipermeable membrane

reverse osmosis in British English
noun: a technique for purifying water, in which pressure is applied to force liquid through a semipermeable membrane in the opposite direction to that in normal osmosis

reverse osmosis in Chemical Engineering
noun: Reverse osmosis is a method of purifying water, in which pressure is used to force a more concentrated liquid through a semipermeable membrane to a less concentrated liquid.