Avant garde and On the sly

On the sly and avant garde are semantically related. in secret topic. In some cases you can use "On the sly" instead an adjective phrase "Avant garde", when it comes to topics like underground.

On the sly adverb - In a furtive manner.

Avant garde and on the sly are semantically related. Sometimes you can use "Avant garde" instead an adjective phrase "On the sly".