reverse osmosis: (chemistry) a method of producing pure water; a solvent passes through a semipermeable membrane in a direction opposite to that for natural osmosis when it is subjected to a hydrostatic pressure greater than the osmotic pressure
osmosis: (biology, chemistry) diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal
halenia: genus of herbs of Eurasia and the Americas: spurred gentians