What does "asthenosphere" mean?

A portion of the Earth's upper mantle, below the lithosphere.

How do you pronounce "asthenosphere"?

Pronounced //asˈθɛnə(ʊ)sfɪə//.

/asˈθɛnə(ʊ)sfɪə/ noun

noun ·Rare ·Advanced level

Noun

1
A portion of the Earth's upper mantle, below the lithosphere.
"Holonyms: upper mantle, outer mantle < mantle < Earth"
2
the lower layer of the crust wordnet

"Holonyms: upper mantle, outer mantle < mantle < Earth"

From astheno- + -sphere.