Abhisamācārika-sīla: 'morality consisting in good behaviour', relates to the external duties of a Bhikkhu such as towards his senior, etc. abhisamācārika-sīla is a name for those moral rules other than the 8 ending with right livelihood i.e. 4-fold right speech, 3-fold right action and right livelihood, as in the 8-fold path Vis.M I; see: sacca IV, 3-5. Impossible is it, o Bhikkhus, that without having fulfilled the law of good behaviour, a Bhikkhu could fulfill the law of genuine pure conduct A.V, 21.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.