noun
grandmother-in-law
Refers to the grandmother of one's spouse. Not a common everyday term; often used in formal or legal contexts.
義祖母はとても優しい方です。
My grandmother-in-law is a very kind person.
Means 'grandmother' (one's own). 義祖母 adds the prefix 義 to indicate the relationship is through marriage.
Compound of 義 (ぎ, 'in-law') and 祖母 (そぼ, 'grandmother'). The prefix 義 is used to indicate a relationship by marriage.