guā-tsóo-hǔ外祖父

one's

one's (maternal) grandfather; one's mother's father

English Wiktionary, “外祖父” (CC BY-SA 4.0) — https://en.wiktionary.org/wiki/%E5%A4%96%E7%A5%96%E7%88%B6 · confidence: Medium (Wiktionary, Hokkien)