What is the antonym for word glacier?

There isn't a perfect one-word antonym for "glacier". However, depending on the context, you could use:

* River: If you're focusing on the movement of water

* Desert: If you're focusing on the lack of ice and water

* Volcano: If you're focusing on heat and activity

* Tundra: If you're focusing on a cold but non-glacial landscape

* Forest: If you're focusing on a lush and vegetative landscape

Ultimately, the best antonym will depend on the specific meaning you want to convey.