Definition of: parsec

(pär′sek) noun Astron.
A unit of length used in expressing the distance of stars. One parsec is almost exactly 206,265 times the mean distance of the earth from the sun, or 19.2 trillion miles, or 3.26 light years. A star is at a distance of one parsec from the earth if its annual parallax amounts to one second of arc (1′′). [<PAR(ALLAX) + SEC(OND)¹ (def. 2)]