I'm unsure if there is any term for this other than "A secretive marriage", but figured I would let you smart forum goers decide.
I am aware of the word
Elope: To run away secretly with the intention of getting married usually without parental consent
However, this states two things that I do not need in the definition. (1) Running away and (2) Hiding it or doing it against the will of one's parents. This implies that the person(s) are of a younger age (likely under 18).
I am looking for a broader term, i.e. These two people have a "insert_here" marriage. Where the term is not limited by age or running away, only that it is secretive. As to why it is secret, it does not necessarily matter, but could include because they share opposite religions that the family members do not approve of, race, ethnicity, social status, etc. Also, the couple does not hide that they are together (dating), but merely does not let others know that they are already married.
Either way, thanks for your help!