What is another term for the fourth pillar?

The Fourth Pillar of Islam is called The Fast of Ramadan.

Fasting is not exclusive to Islam and is a practice very common in many religions, traditional or not.

The fast occurs once a year, during the 9th lunar month, which is called "the month of Ramadan", the 9th month of the Islamic calendar. During this month, according to the Quran itself:

" ... the Quran was sent down as a guidance for the people." (Quran 2:185)

It is also stated that god exempts ill people, travelers and others who would be in conditions unfit for fasting Ramadan.