The term 'silky sound' can be described by two crossword solutions: RUSTLE (6 letters) and SWISH (5 letters). RUSTLE is a sound that is made when something moves quickly through a dry or brittle material, such as leaves or paper. SWISH is a sound that is made when something moves quickly through the air, such as a flag in the wind or a basketball going through a hoop. Both of these sounds are often associated with a smooth, soft, and gentle sound, which is why they are used to describe the term 'silky sound'.