Secular means free of religion. The word is derived from the Medieval Latin word "secularis," which means "worldly." Alternatively, secular can also refer to something that occurs only once every 100 years.
Of the two definitions, the former is the one most widely used. Though secular simply refers to something outside of religion, some more conservative Christian groups use "secular" to refer to anything that is "anti-Christian." Increasingly, occasional references to the term "secular religions" are made. In actuality, the term is a contradiction and is used mostly by religious conservatives to describe groups or organizations that behave like religions but that do not have any sort of common spiritual belief.