(1) The discharge of a fluid material in large amounts from a cavity or surface of the body.diarrhea. (2) Material discharged from the bowels. (3) A material used to remove oxides from the surface of molten metal and to protect it when casting; serves a similar purpose in soldering operations. (4) An ingredient in dental porcelain that by its lower melting temperature helps to bond the silica particles. (5) The moles of a substance crossing through a unit area of a boundary layer or membrane per unit of time. SYN: flux density (1). (6) Bidirectional movement of a substance at a membrane or surface. (7) In diagnostic radiology, photon fluence per unit time. (8) The strength of a field of force (e.g., magnetic) orthogonal to a unit area. (9) The rate of chemical or physical transformation or translocation of a substance per unit time. [L. fluxus, a flow]