What is another word for asthenosphere-?

There isn't really a single, perfect synonym for "asthenosphere" because it's a very specific term referring to the layer of the Earth's mantle. However, here are some words and phrases that capture aspects of the asthenosphere, depending on what you want to emphasize:

General terms:

* Upper mantle: This is a more general term that refers to the entire upper part of the mantle, including the asthenosphere.

* Weak zone: This refers to the asthenosphere's low viscosity and ability to flow.

* Plastic layer: This emphasizes the asthenosphere's ability to deform under pressure.

* Ductile layer: Similar to "plastic layer," this refers to the asthenosphere's ability to flow and bend.

More specific terms:

* Low-velocity zone: This refers to the asthenosphere's lower seismic wave velocities compared to the surrounding mantle.

* Partial melt zone: This refers to the presence of small amounts of molten rock within the asthenosphere, which contributes to its low viscosity.

Ultimately, the best "another word" for asthenosphere depends on the context and what specific characteristic you want to highlight.