1. A term usually applied to flour that, after the milling has stripped it of the wheat germ and other nutritious elements, has niacin, riboflavin and thiamin added back into it. U.S. law requires that flours not containing wheat germ must have these nutrients replenished. 2. The term can also apply to enriching and thickening a sauce with the last-minute addition of an ingredient such as butter, cream or egg yolks.