balsamic vinegar

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An aromatic vinegar of Modena, Italy, made from white Trebbiano grape juice that is heated and aged in wooden barrels for several years.
• noun Any of various similar vinegars.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A dark, sweet vinegar, made from reduced white wine, that has been matured in wooden barrels, the resins of which contribute to its flavour; especially such a vinegar from Modena in Italy.