It's often used in a political or revolutionary context, expressing opposition or rejection of something.
For example:
* "A bas le régime!" (Down with the regime!)
* "A bas la dictature!" (Down with the dictatorship!)
However, it can also be used in a more informal context, such as:
* "A bas les prix!" (Down with the prices!)
It's important to note that "A bas" is a very strong phrase that carries a lot of emotion and can be seen as aggressive or confrontational.