What is "fuzz" in applying patches?

I was applying a patch with quilt in Debian packaging that an error occurred:

Applying patch debian/patches/fixshare.patch
patching file net/slirp.c
Hunk #1 FAILED at 529.
1 out of 1 hunk FAILED -- rejects in file net/slirp.c

I googled it and I've understood that this error is because of "Fuzz" in applying patches. Now, my question is what's fuzz and how can I solve my problem in applying quilt patches?

I've read this article and did the steps that it told, but still I have problem!