Main Entry: ge·oid

Pronunciation: \ˈjē-ˌȯid\

Function: noun

Etymology: German, from Greek geoeidēs earthlike, from gē

Date: 1881

: the surface within or around the earth that is everywhere normal to the direction of gravity and coincides with mean sea level in the oceans

— ge·oi·dal \jē-ˈȯi-d^əl\ adjective