'Periastron' definitions:

Definition of 'Periastron'

From: GCIDE

Periastron \Per`i*as"tron\, n. [NL., fr. Gr. peri` about + 'a`stron a star.] (Astron.) That point, in the real or apparent orbit of one star revolving around another, at which the former is nearest to the latter. [1913 Webster]