The term 'bouncing effect' is often used to describe the phenomenon of sound waves reflecting off a surface and creating an ECHO. The crossword solution for this term is 'ECHO, ' which is a four-letter word. An ECHO is created when sound waves are reflected off a surface, such as a wall or a canyon, and then return to the listener's ears. This creates a reverberation that can be heard multiple times, creating the bouncing effect.