[light-year] n (1888) 1: a unit of length in astronomy equal to the distance that light travels in one year in a vacuum or about 5.88 trillion miles (9.46 trillion kilometers)
2: an extremely large measure of comparison (as of distance, time, or quality) "seems like light-years ago" "has light-years more talent" "two minutes and yet ~s away from the crowded village --Suzanne Patterson"