from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The apparent radius of a celestial body when viewed as a disk from Earth.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The apparent radius of a star etc, when viewed from Earth
- n. radius, half of a diameter
from the GNU version of the Collaborative International Dictionary of English
- n. Half of a diameter; a right line, or the length of a right line, drawn from the center of a circle, a sphere, or other curved figure, to its circumference or periphery; a radius.
from The Century Dictionary and Cyclopedia
- n. One half the diameter: especially, in astronomy, one half the angular diameter of the sun, moon, or other object showing a disk; the radius.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the apparent radius of a celestial body when viewed as a disc from the earth
semi- + diameter (Wiktionary)