Behind or alongside a hotel's reception desk there is often a display board that shows, one above the other, the different standards of accommodation available in the hotel with a nightly rate beside each one (single, double, suite etc). I am told that the board used to be called 'the rack', hence the term 'rack rate'. At many hotels it is possible to get a considerable reduction on those rates, but at times of high demand you may end up having to pay the full rack rate. As it happens, I'm going through one of those battles at the moment!