The description of the word you requested from the astronomical dictionary is given below.
Gè = [Greek] Earth; kentrum = [Greek] center, middle
Geocentric means it has something to do with the center of the Earth.
Geocentric coordinate systems have the center of the Earth for their origin, and are almost always rectangular coordinate systems, but can vary in the directions of the coordinate axes. Oft-used geocentric coordinate systems are the equatorial geocentric coordinate system and the ecliptic geocentric coordinate system.