The term DEFLATING SOUND can be summarized by three crossword solutions: PFFT (4 letters), SSS (3 letters), and SSSS (4 letters). PFFT is an onomatopoeia used to represent a sound made when air is released quickly, such as when a balloon is deflated. SSS is an onomatopoeia used to represent a hissing sound, which could be heard when air is slowly released from a balloon. Lastly, SSSS is an onomatopoeia used to represent a sound made when air is released in a steady stream, such as when a tire is deflating. All three of these sounds are associated with the term DEFLATING SOUND.