This tongue-twister actually means something that’s hard to contest indeed: “40 is 40” (сы шы шы сы шы). Chinese have brains of supercomputers: there’s a fairy-tale of some kind that’s composed entirely of these two syllables (okay, in different tones), and Chinese claim that all native speakers can easily understand what every one of those sounds means just from its context. Try it: 十四是十四, 四十是四十. Click on a link and click the “listen” button.
I tried it twice: in a group of Chinese folks, say a random combination of these sounds (never mind the tones) and they will all applaud and laugh thinking you got it, but then you can easily get them puzzled saying that you just made it up and a combination was truly random. Chinese tend to second-guess tones for foreigners, so I guess any random combination of those sounds you make, actually makes sense if they figure out the right tones for you.
Some statistics: there are 86 characters (and thus even more meanings) that correspond to shi. My small dictionary only shows 32 on only 7 pages. I guess I’ll only ever learn at most 37% of magic that this word has.