noun Date: 1888 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), an extremely large measure of comparison (as of distance, time, or quality)
LIGHT-YEAR
Meaning of LIGHT-YEAR in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012