Vocabulary What does 小石 (こいし, koishi) mean? 小石 (こいし, koishi) means pebble; small stone. Quick factsReadingこいしRomajikoishiPart of speechnoun 小石こいしkoishipebble; small stone1noun pebble; small stoneAlso written: 礫Kanji in this word小small, little石stone