Trub (pronounced chroob) is a beer brewing term for solids that exist in a yeast propagator, fermenter or aging tank that aren't yeast. The solids that remain to be transferred to a fermenter are usually small particles of malt, adjunct and hops. Trub is measured by centrifuging a sample of fermenting beer, some trub is heavier than yeast and some is lighter, and both have a different colour and consistancy than yeast, so the sample will separate into layers.
Home brewers often refer to all solids (including yeast in a fermenter as being trub, however trub consists of hot break, cold break and tiny pieces of hops and barley malt. This is because in home brewing the yeast (which is still alive after finishing fermentation) is usually discarded while in large scale brewing it is often collected and re-pitched. If you brewed wine, the solids would be called "lees".