三さん角かく筋きんさんかくきんMeanings1noundeltoid muscle; deltoidAnatomical term for the triangular shoulder muscle.三さん角かく筋きんは肩かたの大おおきな筋きん肉にくです。The deltoid is a large muscle of the shoulder.三さん角かく筋きんを鍛きたえると肩かた幅はばが広ひろく見みえます。Training the deltoids makes the shoulders look broader.