It depends on which country you`re from. Different Arabic countries have different dialects, and therefore, different words that mean grandma and grandpa. For grandpa, some say ''jidd'', and some say ''seed''. For grandma, ''sitt' or ''jiddah''. This is what I know. I`m sure there are other words out there.
If you`re asking about Arabic fusha, it`s ''jidd'' and ''jiddah'' for grandpa and grandma, respectively.
:arabi1: