A better word is "unfalsifiable". String theory predicts numbers other spatial dimensions. (at least 11) You can test for these. However, these extra dimension

A better word is "unfalsifiable". String theory predicts numbers other spatial dimensions. (at least 11) You can test for these. However, these extra dimensions can be arbitrarily small. You can prove that no extra dimensions greater than 1e-30m (or whatever) exist. This does not disprove string theory. Well, now you have to test for smaller extra dimensions. Let's say you prove no dimensions larger than 1e-40m exist. Still haven't disproven string theory: they could be smaller. So on and so forth. These extra dimensions have to curl up. The way in which these extra dimensions curl up constrain the masses and properties of the various particles. There are a stupidly large number of different ways these extra dimensions can curl up. Something like 10^500. So there's no way to measure the various properties of physics and the universe in a way that falsifies string theory. Regardless of what experiments show, there are still going to be an immense number of curlings that are consistent with the measured reality. IMHO string theory is still science, but it's depressing, fruitless, dystopian science. It lacks... hope.