the GNU version of the Collaborative International Dictionary of English
n. A pilgrimage to Mecca; every Muslim must make this journey at least once.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the fifth pillar of Islam is a pilgrimage to Mecca during the month of Dhu al-Hijja; at least once in a lifetime a Muslim is expected to make a religious journey to Mecca and the Kaaba
Word Usage
"The haj is the pilgrimage to Mecca that all Muslims are obliged to make at least once in their lives if they are able."