from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A geoisotherm of equal mean summer temperature.
from the GNU version of the Collaborative International Dictionary of English
- n. A line connecting points on the earth's surface having the same mean summer temperature.
from The Century Dictionary and Cyclopedia
- n. An imaginary line over the earth's surface passing through points which have the same mean summer temperature.
Sorry, no etymologies found.