The term 'hollow sounds' can be summarized by the crossword solution 'THUDS, ' which is a five-letter word. THUDS are loud, low-pitched noises that are often associated with impacts or collisions. They are usually created when something solid strikes a surface or object, and the sound is hollow because it is created in an enclosed space. THUDS are commonly heard in everyday life, such as when someone slams a door or drops a heavy object.