What are the precise definitions of firriqab, al-gharimin, fisabilillah and ibnu sabil as zakat recipient categories?

Summary

The Syariah Committee of Penang defined these four categories. Firriqab covers those freeing themselves from bondage, including liberation from ignorance and war captivity, and per the Al-Manar commentary it may be used to help Muslim peoples free themselves from colonial rule. Al-gharimin are debtors in three cases: reconciling disputing parties, debt for personal needs that were permissible or impermissible but the debtor has repented, and guaranteeing another's debt when both are unable to pay. Ibnu sabil is a traveller who has run out of funds on a permissible journey, while fisabilillah is understood in its general sense, covering all good works pleasing to Allah such as building mosques and religious schools.

Written in our own words from the original fatwa — check the source before acting on it.