Wiktionary
n. The mother of one's mother.
Usage examples of "maternal grandmother".
She is back in the highlands of Guatemala, six years old, her maternal grandmother by her side.
And so to you personally, dear reader, who are no doubt leading a muddled kind of life outside this institution, to you my friends and weekly visitors who suspect nothing of my paper supply, I introduce Oskar's maternal grandmother.
Her maternal grandmother was a Sunrunner before Prince Sinar of Kierst winked at her and carried her away to his island.
I have even been informed, that at Paris she discovered a relation of her own, no less a person than her maternal grandmother, who was not by any means a Montmorenci, but a hideous old box-opener at a theatre on the Boulevards.
But they just say the name is an English version of the Hebrew Hannah and that Hannah was the name of the prophet Samuel's mother and also Christ's maternal grandmother.
Dickson's mutterings hadn't registered with me on that frantic day, and I realized now that he had immediately seen that the twins were the spit and image of their maternal grandmother.