astronomical unit

WordReference Random House Learner's Dictionary of American English © 2025

as•troˈnom•i•cal ˈu•nit, n. [countable]

1. Astronomy a unit of length, equal to the distance of the earth from the sun: about 93 million miles (150 million km).Abbr.: AU

WordReference Random House Unabridged Dictionary of American English © 2025

as′tronom′ical u′nit, [Astron.]

1. Astronomy a unit of length, equal to the mean distance of the earth from the sun: approximately 93 million miles (150 million km). Abbr.: AU

• 1900–05

Collins Concise English Dictionary © HarperCollins Publishers::

astronomical unit noun

1. a unit of distance used in astronomy equal to the mean distance between the earth and the sun. 1 astronomical unit is equivalent to 1.495 × 10¹¹ metres or about 9.3 × 10⁷ miles