Short definition
Warm aromas of toasted bread, brioche, or caramel in wine, usually from oak aging or lees contact.
That fresh-baked-bread smell in aged Champagne? Toastiness from years of contact with dead yeast cells (lees). In still wines, toasty notes come from barrels that were heated during construction. The level of toast — light, medium, heavy — is a choice the winemaker makes. Toasty wines match well with dishes that have browned, caramelized, or roasted elements.