Vocabulary What does 大きさ (おおきさ, ookisa) mean? 大きさ (おおきさ, ookisa) means size; dimensions; volume. Quick factsReadingおおきさRomajiookisaPart of speechnoun 大きさおおきさookisasize; dimensions; volume1noun size; dimensions; volumeKanji in this word大big, large