What is an antonym for liter?

There isn't a direct antonym for "liter" in the sense of a unit of volume. However, depending on the context, you could use words like:

* Small: if you're contrasting a liter with a smaller unit of volume like milliliter.

* Large: if you're contrasting a liter with a larger unit of volume like gallon.

* Empty: if you're talking about the absence of liquid in a container that can hold a liter.

* Full: if you're talking about the presence of liquid in a container that can hold a liter.

It would be helpful to know the specific context in which you need an antonym for "liter" to give you a more accurate answer.