Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
The haram haircut in Islam is called qaza` which is to shave parts of the head and leave the others.
Answering your question, Dr. Mohammad S. Alrahawan, Associate Professor at the department of Islamic Studies in English, Al-Azhar University, Egypt, states:
On the authority of Ibn `Umar (may Allah be pleased with him) who said, “The Messenger of Allah (peace be upon him) forbade qaza`. Qaza` means having part of a boy’s head shaved and leaving part unshaven.
This Hadith clearly states the prohibition of qaza` which is to shave parts of the head and leave the others. Meanwhile, if one has his hair cut in such a manner that there is a very clear difference between one part of one’s head and another, then this is also qaza`.
Almighty Allah knows best.