/luyt"year', -year"/ , n.
1. Astron. the distance traversed by light in one mean solar year, about 5.88 trillion mi. (9.46 trillion km): used as a unit in measuring stellar distances. Abbr.: lt-yr
2. light-years ,
a. a very great distance, esp. in development or progress: The new computer is light-years ahead of the old one.
b. a very long time: It's been light-years since I've seen my childhood friends.
[ 1885-90 ]