I was wondering, how would you best describe the sound a zip fastener makes when it's opened or closed slowly? You know, that "r-r-r-r-r" kind of sound?
I thought about growling, but that feels too violent a choice.
I will go with ri[iii...]ri[iii...]
If saying RIRI out loud approximates a zipper-like sound, then yes, it's onomatopoeic. However, I do not hear RIRI in American zippers. Our little plastic-coiled ones for ladies-wear and the big brass ones for 501 Levis and the three-yard long monster-toothed zipper on my camping text all have looong zzzzipzs that the short syllables of RIRI does not seem to represent.
If you are doing a radio ad or TV promo, you don't have to write the RIRI brand. Just record the zipper (going at various speeds) and have a good novelty voice-over say RIIIIIIIIIRIIIIIIIIII, sustaining for the length of the zip, sort of like the insurance co. that has trained us to hear a duck say quack quack but with a distinct "AFLAC" coming through -- the name of the firm. Quora
the word itself is onomatopoeic the noise closing a zipper makes is a zip sound.
Zziiipppp but perhaps only when closed quickly. you could also argue that it is like a growl or i prefer a purr when a zipper is closed slowly.