from The Century Dictionary.
- noun In geom., a line subtending or stretching across; the chord of an are; a line opposite to an angle spoken of.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Geom.) A line subtending, or stretching across; a chord.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun geometry A line which
subtends, especially the chordof an arc.
- noun geometry The
anglesubtended by a line at a point.
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.