from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A line which subtends, especially the chord of an arc.
- n. The angle subtended by a line at a point.
from the GNU version of the Collaborative International Dictionary of English
- n. A line subtending, or stretching across; a chord.
from The Century Dictionary and Cyclopedia
- n. In geom., a line subtending or stretching across; the chord of an are; a line opposite to an angle spoken of.
Sorry, no etymologies found.
A rough calculation based on an angular subtense of 1/2 degree and a distance of 30,000 feet suggests that the shadow would be wholly washed out.