asthenosphere definitions

WordNet (r) 3.0 (2005)

n
1: the lower layer of the crust

Merriam Webster's

noun Etymology: Greek asthen?s weak + English -o- + sphere Date: 1914 a zone of a celestial body (as the earth) which lies beneath the lithosphere and within which the material is believed to yield readily to persistent stresses • asthenospheric adjective