The point is that some grammatical patterns leave most of the work to the imagination of the reader (or listener). A famous example of this is the English "noun noun" pattern. Some examples are easy:
joke book = book of jokes
history book = book about history
These are easy because they're familiar - we already know them, and we know what they mean. But what about "chair book"? It could mean all sorts of things:
book about chairs (compare: history book, fashion book)
book to read in a chair (compare: loo book, kitchen book)
book to prop up a chair with a missing leg
and so on and on.
Where do these meanings come from? The answer: our imagination. What you look for when you read "chair book" is a link between the two ideas "book" and "chair". Nobody tells you what that link is or what kind of link it should be. You're on your own, and can make up any link you like.
Back to pedagogy and a bored class in need of creativity. Ten-minute starter activities work well here. Why not give students a couple of nouns to be fitted together with as many different meanings as possible? They could do it in class or in groups, and there could be a prize for the most meanings or the most outlandish meaning. Then you could swap roles - they think up word-pairs and you provide a meaning - if you can. They may turn out to be better than you think.
If it gets out of hand you can always turn it into a useful grammar lesson.
In all these pairs, it's the first noun that modifies the second, so the pattern is like this:
This rule is very general and very important, but a famous study found that a lot of English speakers aren't aware of it. Many school-leavers thought that a bird tree could be a bird in a tree; but university graduates (regardless of subject) knew better. In one lesson you could bring your fantasy class (meaning what? You decide!) up to the level of university graduates - and stretch their imaginations at the same time.
Richard Hudson is professor of linguistics at University College, London Geoff Barton is headteacher of King Edward VISchool, Bury St Edmunds, Suffolk