What is the meaning of "al-Ahzab" in the Qur'an?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

'al-Ahzab' is the plural of 'Hezb', which means party and faction. From linguistic point of view, 'al-Tahazzub' means coming together and assembly, whether it aims at good/bad goals, in persons or ideas. The term 'al-Ahzab' is mentioned in the Qur'an with different meanings. Here are the most important of those meanings:
1) Those people who gathered to fight the Prophet (Sallallahu Alaihi wa Sallam) and Islamic Da'wah.
Allah Says (interpretation of meaning): {And when the believers saw Al-Ahzab (the Confederates), they said: "This is what Allah and His Messenger (Muhammad (Sallallahu Alaihi wa Sallam) had promised us; and Allah and His Messenger (Muhammad (Sallallahu Alaihi wa Sallam) had spoken the truth. …} [33:32].
2) Those people who are assembled and joined to follow the Devil's way of life.
Allah Says (interpretation of meaning): {Shaitan (Satan) has overpowered them. So he has made them forget the remembrance of Allah. They are the party of Shaitan (Satan). Verily, it is the party of Shaitan (Satan) that will be the losers!} [58:19].
3) Those people who constitute one entity and follow the Islamic way of life as practiced by the Sahabah, their followers and those who follow them.
Allah Says (interpretation of meaning): {… They are the Party of Allah. Verily, it is the Party of Allah that will be the successful.} [58:22].
4) The non-Muslim nations those came before the advent of Islam; those who denied the Divine messages.
Allah Says (interpretation of meaning): {Before them (were many who) belied (Messengers) - the people of Nuh (Noah); and 'Ad; and Fir'aun (Pharaoh) the man of stakes (with which he used to punish the people). And Thamud, and the people of Lut (Lot), and the Dwellers of the Wood: such were the Confederates.} [38:12-13].
Finally, the word 'Hezb' (single of Ahzab) means half a Juz' of the Qur'an; the Qur'an consists of 30 Juz' and each Juz' consists of two Hezb, i.e. there are sixty Hezb in the Qur'an.
Furthermore, classifying the Qur'an into sixty Hezb is an idiomatic matter and it is used in principle in Mauritania, Tunisia, Morocco, Libya, Algeria and other African countries.
Allah knows best.