曾祖母 Sousobo is proper, but as a foreigner I've always heard
曾お祖母さん Hiiobaasan
Tatarabuela Grandmother: abuela Great grandmother: bisabuela Great great grandmother: tatarabuela
bisabuela
its grandmother http://www.kidlink.org/KIDPROJ/grandmother/japan.html
bisabuela
Tatarabuela rebisabuela Bisabuela --- great grandmother
obaachan
Tatarabuela Grandmother: abuela Great grandmother: bisabuela Great great grandmother: tatarabuela
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Your grandmother's mother is your great grandmother and your son's great-great-grandmother.
Heiwa no sobo no nokor
The Welsh term for 'great grandmother' is "nain fawr".
Your great great grandmother's sister is your great great grandaunt, some would say great great greataunt.
bisabuela
In Portuguese, "great grandmother" is translated as "bisavó".
You would say "oumagrootjie" in Afrikaans to refer to your great grandmother.
Great grandmother in Polish is pronounced as "prababcia".
Your great grandmother's sister is your great great aunt (or some would say, your great grand aunt).