If "underground" refers to a physical location:
* Aboveground: This is the most direct opposite, indicating a location above the surface of the earth.
* Surface: This also refers to a location on the surface of the earth.
* Overground: Similar to aboveground, but emphasizes the contrast with an underground location.
If "underground" refers to something hidden or secret:
* Overt: This means open and obvious, the opposite of hidden.
* Public: This refers to something accessible to everyone, the opposite of something secret.
* Official: This refers to something sanctioned and known, the opposite of something clandestine.
If "underground" refers to a subculture or movement:
* Mainstream: This refers to the dominant culture or popular trends.
* Established: This refers to something recognized and accepted, the opposite of something new and alternative.
In some contexts, "aboveground" may be the most appropriate opposite.
For example:
* "The concert was held in an underground club." (Opposite: The concert was held in an aboveground venue.)
* "The band had a large underground following." (Opposite: The band achieved aboveground success.)
It's important to consider the specific context of the sentence to determine the best opposite for "underground."