There are 19 meanings listed in OED's entry for the word secular, two of which are labelled obsolete. See ‘Meaning & use’ for definitions, usage, and quotation evidence.
secular, adj. & n. meanings, etymology and more | Oxford English Dictionary
In contemporary English, secular is primarily used to distinguish something (such as an attitude, belief, or position) that is not specifically religious or sectarian in nature (for example, music with no religious connection or affiliation might be described as "secular").
SECULAR definition: of or relating to worldly things or to things that are not regarded as religious, spiritual, or sacred; temporal. See examples of secular used in a sentence.
Add to word list not having any connection with religion: secular society / music / education (Definition of secular from the Cambridge Academic Content Dictionary © Cambridge University Press)
Anything not affiliated with a church or faith can be called secular. Non-religious people can be called atheists or agnostics, but to describe things, activities, or attitudes that have nothing to do with religion, you can use the word secular.
Secularity or secularness (from Latin sæculum, 'worldly' or 'of a generation' or 'century') is the state of being unrelated to, or neutral in regard to, religion. The origins of secularity as a concept can be traced to the Bible, and it was fleshed out through Christian history into the modern era. [1] .
You use secular to describe things that have no connection with religion. He spoke about preserving the country as a secular state. ...secular and religious education.