المعنى الاصطلاحي :

Those who come after the first three best generations (since the start of the Islamic era) and pursue the path of the people of religious innovations and deviant whims.

الشرح المختصر :

The word "Al-khalaf" is the opposite of "As-salaf". It refers to someone accused of innovation in religion, or known by an unpleasant title. Anyone who deviates from the Qur'an and the Sunnah, and diverts from the path of the Companions, may Allah be pleased with them, and doesn't adopt their way of life; he is called "khalafi" even if he lived amongst the Companions. The term also refers to those who have gone astray from the guidance of the Prophet, may Allah's peace and blessings be upon him, and his Companions in creed issues, from amongst people of innovations and deviant whims, such as the Kharijites and Rafidah; or scholastic theologians, who give preference to the reason over the Shar`iee texts, such as Al-Jahmiyyah, Al-Mu`tazilah, Al-Asha`irah, Al-Qadariyyah, Al-Murji'ah and the likes. Therefore, anyone who follows the methodology of the "khalaf" is called "khalafi", and they actually approve this title for themselves. Even most of them courageously prefer the way of the "Khalaf" over that of the "Salaf". Their methodology is based upon extracting diverted meanings from the texts by using far possible meanings and unusual language.

التعريف اللغوي المختصر :

"Al-khalaf": the later one, and anyone who come after those who passed away, or those who come after the preceding generation in terms of time or status. Other meanings: alternative or substitution.