Short definition
A rich, creamy flavor in wine, usually from malolactic fermentation converting sharp acid into softer lactic acid.
That butter-and-cream flavor in many California Chardonnays comes from malolactic fermentation, not actual butter. The process converts tart malic acid into softer lactic acid, plus a compound called diacetyl — literally the same molecule in movie-theater popcorn butter. Winemakers who skip "malo" keep the wine lean and crisp instead.