Japanese More information Kanji in this term ... Kanji in this term 精 巣 せいGrade: 5 そうGrade: 4 on'yomi Close More information Alternative spelling ... Alternative spelling 精巢 (kyūjitai) Close Pronunciation IPA(key): [se̞ːso̞ː] Noun 精(せい)巣(そう) • (seisō) testicle Synonyms 睾丸(こうがん) (kōgan) Wikiwand - on Seamless Wikipedia browsing. On steroids.