杵臼之交 chǔjiùzhījiāo unlikely friendship Origin Definitions Defs Strokes Stroke Words Sentences Sents 杵臼 chǔjiù mortar and pestle A pestle and mortar; tools used for pounding or grinding materials.之 zhī particle [possessive] Connects a describing word or phrase to the noun it describes, similar to 的 de but used in formal or literary writing.交 jiāo noun friendship Friendship; social or diplomatic relations