from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A line drawn on a map connecting points that receive equal amounts of sunlight.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A line of equal or constant solar radiation.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. an isogram connecting points receiving equal amounts of sunshine
iso- + Greek hēlios, sun; see sāwel- in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)
iso- and Ancient Greek ἥλιος (helios, "sun"). (Wiktionary)