The term LEAK SOUND can be broken down into four crossword solutions: HISS (4 letters), DRIP (4 letters), SSS (3 letters), and SSSS (4 letters). HISS is a sound made by a snake or other reptile, and is also used to express disapproval. DRIP is the sound of liquid falling drop by drop, such as water dripping from a faucet. SSS is an onomatopoeic word used to describe a hissing sound, while SSSS is a longer version of the same sound.