(Naskh). Abrogation or repeal. Certain Qur'anic verses were abrogated during the lifetime of the Holy Prophet Muhammad (May the Salutations of Allah be upon him and Peace). The People of the higher teaching regard these as postponed rather than abrogated texts - that is, they were postponed until the time arrived when mankind had reached a higher level of knowledge. With this high knowledge he could then implement the message of those particular verses.
Islam means peace and the person who follows this peace is called the Muslim. From another root meaning of the word, Islam means complete submission and surrender, and the person who submits and surrenders himself to the will of his Lord is the person who has accepted Allah as his Creator, Sustainer, Lord and the Master of the Day of Judgement.
So from both the definitions Islam means a way of life for people who have opted to follow peace as opposed to chaos, order as opposed to disorder, discipline as opposed to indiscipline, submission as opposed to refusal, surrender as opposed to insolence, obedience as opposed to disobedience etc. All these things combined together to define Islam as away of life by which a person becomes a follower of peace and not a follower of chaos. And the followers of peace are the Muslims whose duty it is: "to establish peace and what is good, and to prevent chaos and what is evil, and they are the best people." (Al-Qur'an 3:110)