parsec noun.
['pɑ:sɛk] E20.[from PAR(ALLAX + SEC(OND noun1.]Astronomy. A unit of length equal to the distance at which a star would have a heliocentric parallax of one second of arc, approx. equal to 3.09
1016 metres (19.2 1012 miles, 3.26 light-years). [TahlilGaran] English Dictionary ▲