What does "flux" mean?

Additional senses

1. 2.The state of beinng liquid through heat; fusion.
2. 3.(Chem.& Metal.) Any substance or mixture used to promote the fusion of metals or minerals, as alkalies, borax, lime, fluorite. Note: White flux is the residuum of the combustion of a mixture of equal parts of niter and tartar. It consists chiefly of the carbonate of potassium, and is white.- Black flux is the ressiduum of the combustion of one part of niter and two of tartar, and consists essentially of a mixture of potassium carbonate and charcoal.
3. 4.(Med.) (a) A fluid discharge from the bowels or other part; especially, an excessive and morbid discharge; as, the bloody flux or dysentery. See Bloody flux. (b) The matter thus discharged.
4. 5.(Physics) The quantity of a fluid that crosses a unit area of a given surface in a unit of time.
5. 6.Flowing; unstable; inconstant; variable. The flux nature of all things here. Barrow.
6. 7.To affect, or bring to a certain state, by flux. He might fashionably and genteelly . . . have been dueled or fluxed into another world. South.
7. 8.To cause to become fluid; to fuse. Kirwan.
8. 9.(Med.) To cause a discharge from; to purge.