大洞 (dà dòng) is a place name (toponym) literally meaning 'big cave' or 'great cave'. The source data for this row is incomplete — the English gloss is missing (just '#') and the pinyin field shows only 'dà' instead of 'dà dòng'. This entry likely refers to a specific location such as 大洞镇 in Guangdong or a cave sight, but the meaning cannot be confirmed from the given data. Use with caution.