If food is scrummy, it tastes very good — the kind of good that makes you want another bite. It is warm, informal British English, a little childish or fond, the word a parent might use about cake, or a friend about a pudding. You would not put it in a serious restaurant review, and you would not use it for a stiff dinner speech. It is almost always about food and drink, not about people or ideas, though someone might stretch it as a joke. It sits next to yummy and delicious, but it has a British kitchen feel that delicious does not. Speakers outside Britain may not use it at all. Though actually, it has nothing to do with a rugby scrum, even though it looks as if it might.