Based on thesaurus.com the synonyms for secular are civil, materialistic, worldly, lay, material, profane, temporal, earthly, non-religious, unsacred, nonreligious, nonclerical, off this world.
To determine which could be the best synonym for the secular depends upon which the synonym word is applied. It can give significance to the use of the word if it is placed properly to provide the real meaning intended.
