Imagine a situation where you've been invited to dinner at a friend's place. You're extremely hungry but you learn that the dinner won't be ready for another half an hour. So you decide to eat an apple or a bite of bread or some other small thing which will not satisfy your hunger fully, but will temporarily make it more tolerable. Is there a word/phrase/idiom to describe this small snack prior to a big meal?
The Russian equivalent of what I am looking for is заморить червячка, which literally means to starve/kill the little worm. The only translation I found of this idiom was to stay one's hunger. However, I couldn't find any usage examples of it and the google query for define:to stay one's hunger doesn't return anything useful, so I guess this idiom, if used at all, isn't very common.