means that juice for wine is cooked immediately after the grapes have been crushed. According to Jewish law, mevushal wines can be served by non-Sabbath observing Jewish individuals and other people not of the Jewish faith.
Cooked. Most often relevant to cooked (pasteurized) grape juice and wine which has fewer restrictions than non-pasturized. Also has relevance for cooked food for Shabbos (Saturday).
Cooked, to distinguish from baked, fried or roasted. There has to be a liquid (so "boiled" is near the mark, but something can be mevushal at below boiling point).