Here is dictionary.com's definition of secular:
sec·u·lar:–adjective
1. of or pertaining to worldly things or to things that are not regarded as religious, spiritual, or sacred; temporal: secular interests.
2. not pertaining to or connected with religion (opposed to sacred): secular music.
3. (of education, a school, etc.) concerned with nonreligious subjects.
4. (of members of the clergy) not belonging to a religious order; not bound by monastic vows (opposed to regular).
5. occurring or celebrated once in an age or century: the secular games of Rome.
6. going on from age to age; continuing through long ages.
–noun 7. a layperson.
8. one of the secular clergy.
I hope that helps.