Ceremonially clean, according to Jewish law; -- applied to food, esp. to meat of animals slaughtered according to the requirements of Jewish law. Opposed to tref. For food to be officially kosher, it must be certified fit to eat by a Rabbi, according to Jewish ritual law; as, kosher food.
designating a shop, store, house, etc., where such food is sold or used; as, a kosher restaurant.
Proper; seemly; appropriate; legitimate; as, it's not kosher to do it that way.