Longman Dictionary English From Longman Dictionary of Contemporary EnglishRelated topics: Astronomyastro-astro- /æstrəʊ, -trə $ -troʊ, -trə/ prefix XXrelating to the stars, the planets, or space an astronaut (=someone who travels in space) astronomy (=scientific study of the stars)Origin astro- Old French Latin, from Greek, from astron “star” ldoceonline.com