n. (pl. apsides) either of two points on the orbit of a planet or satellite that are nearest to or furthest from the body round which it moves. apsidal adj.
[ L f. Gk (h)apsis, -idos arch, vault ]
APSIS
Meaning of APSIS in English
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012