When a bottle of red wine (and, to a lesser extent, some white wines) ages, it accumulates or "throws off" sediment. Sediment consists of tannin, pigments, and other trace particles that solidify over time and sink to the bottom of the bottle. To avoid getting the bitter sediment in your wineglass, decant an old bottle of red before serving. Sediment can also refer to any solid matter that settles out of wine during the various stages of the winemaking process. See also lees.