Au sec is a French culinary term that translates to "almost dry".
Au sec is a rough measurement, usually used in sauce-making. Liquid, such as wine, evapourates when added to a hot pan. Au sec refers to the amount of liquid remaining.
Due to the small amount of liquid desired, it is easy for the preparer to misjudge the heat. This opens the potential to totally evapourate all liquid or scorch the ingredients. If this happens, more liquid can be added but the flavour will change.