noun
grandaunt; great-aunt
Refers to the sister of one's grandparent. The kanji 大叔母 is more common, while 大伯母 is a variant.
私の大叔母は今年で90歳になります。
My grandaunt will turn 90 this year.
大叔母から昔の写真をもらった。
I received old photos from my great-aunt.
Compound of 大 (おお, 'great') + 叔母 (おば, 'aunt'), literally 'great aunt'. The reading おおおば is a straightforward combination of the readings of the components.