what means is defined in DSO /lib64/libz.so.1

Hi , I found this error /usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/4.7.0/../../../../lib64/libgpac_static.a(base_encoding.o): undefined reference to symbol 'deflate' /usr/bin/ld: note: 'deflate' is defined in DSO /lib64/libz.so.1 so try adding it to the linker command line /lib64/libz.so.1: could not read symbols: Invalid operation collect2: error: ld returned 1 exit status Could someone help me , to understand what happens ? Thanks in advance, -- Sérgio M. B.